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Know a little something about maintenance, fixing, tuning, or modifying MX, offroad, & dual sport motorcycles, ATV or UTV? Or, maybe you have mad skills riding or racing them? Whatever the case, if you have valuable knowledge & experiences that relates to motorcycles, ATVs, or UTVs, please help your fellow riders by sharing your best tips, tricks, and how to articles.

    Kevin from Wiseco
    Find out how to relieve an exhaust bridge and drill lubrication holes in 2 stroke applications, so you can get the most out of your piston!
    When you order a new Wiseco 2-stroke piston and open up the box and read the instructions, you might see something like “follow these steps to drill the lubrication holes.” There’s no doubt that the thought of drilling holes in your new piston can be scary and intimidating. But not to worry! We’ll get you through it right here with all the information you need and a step-by-step. Relieving the exhaust bridge and drilling lubrication holes is a common part of the 2-stroke top end replacement process, but the importance of performing these steps is unrealized by many and neglected too often.

    Drilling lubrication holes is a simple but important process for many 2 stroke applications.
    So, what is an exhaust bridge?
    First things first, not all 2-stroke cylinders have an exhaust bridge. So if your cylinder does not have one, drilling holes in your piston is not necessary.
    The exhaust bridge is the thin strip of metal that separates the exhaust ports in the cylinder. Whether you look into the exhaust ports through the exhaust outlet or through the cylinder bore, if you see a thin metal wall separating your exhaust ports, that is your exhaust bridge. For the purpose of installing a new Wiseco piston, the area of concern is the edge of the exhaust bridge on the inside of the cylinder bore.

    The exhaust bridge is the edge of the wall separating the exhaust ports on some 2 stroke cylinders.
    Why do I need to relieve the exhaust bridge?
    Now that we know what the exhaust bridge is, it’s important to understand why we feel this machine work is essential to replacing a 2-stroke top end. The most heat in your motor is generated from combustion in the cylinder during normal operation. Specifically, the exhaust port(s) of the cylinder are exposed to the most heat because this is the only way out for the hot gas produced during combustion. This means that under normal running conditions, your piston and your exhaust bridge are constantly under the pressure of extreme heat.
    Wiseco pistons are made from forged aluminum, which offers more strength and reliability, but also expands faster under heat than an OEM cast piston. The exhaust bridge will also expand more than the rest of the cylinder because it is such a thin structure. The lack of material makes it harder for heat to dissipate before it affects the aluminum and causes expansion. 
    Expansion under heat is normal, but must be compensated for to make sure you get the most life and best performance out of your top end. Relieving the exhaust bridge simply means taking a small amount of material off the face the bridge in order to make room for expansion. If there wasn't any extra clearance, the exhaust bridge would expand past the cylinder wall once your motor heats up. This leads to scoring on the piston as it comes into contact with the exhaust bridge, especially as the piston expands at the same time.

    Notice the small amount of material taken off of the exhaust bridge, and the blending back into the cylinder. Read below on how to accomplish this.
    Relieving the Exhaust Bridge
    Now that we have some understanding established, let’s go through how to get it done. As always, if you don’t feel comfortable doing this work, this can commonly be done by the shop performing your cylinder work. If you have the rights tools, this can be done in the garage on cast iron and steel cylinder bore liners. We recommend using a die grinder with a small sanding roll to gently remove .003” of material off the cylinder wall face of the exhaust bridge.
    After the material is removed, the machining must be blended with the rest of the cylinder wall at the top and bottom of the exhaust bridge. You want to make sure there’s an easy slope for the piston ring to slide over when entering and exiting the exhaust bridge relief. If your cylinder is lined with Nikasil, this process will not work because that material is too hard. Your exhaust bridge must be relieved before being lined with Nikasil to achieve the same result. Check with the shop you choose for your cylinder work if you are unsure.
    Why do I need to drill holes in my piston?
    Relieving the exhaust bridge will make sure there’s no expansion past the cylinder wall, but we still want to make sure we keep the heat as low as possible. With small holes drilled into the skirt of the piston, oil underneath the piston will makes its way through the holes, and lubricate the contact point between the piston and exhaust bridge. Better lubrication means less friction, and less friction means less heat, which is what we want to make sure we don’t have any abnormal wear.
    Drilling Lubrication Holes
    Make sure you have the instruction sheet that came with your new piston. This drilling information can also be found there, complete with a visual diagram.

    Be prepared with your instruction sheet.
    1. Install the piston and wrist pin on the connecting rod with one circlip. Make sure the arrow stamped on the dome of the piston is facing the exhaust side of the cylinder.
    2. Slide the cylinder over the piston until the cylinder is in its normal position on the crankcase.

    Temporarily install the piston on the connecting rod and slide the cylinder over the piston.
    3. Slowly turn the engine over until the bottom ring groove (or the only ring groove if your piston has only one) on the piston is at the top of the exhaust bridge. You can look through the exhaust port of the cylinder to help know when the piston is in the correct spot.
    4. Go through the exhaust port with a pencil and trace a line on the piston skirt for each side of the exhaust bridge.

    Trace two lines on the piston, one on each side of the exhaust bridge.
    5. Once the lines are traced and visible, remove the cylinder and the piston.
    6. Start .300” below the bottom ring groove and mark two points .375” apart from each other. Make sure the points are centered horizontally between the two lines you traced.
     
    Use the proper measurements to mark 2 points for the holes to be drilled.
    7. Drill two holes .060” - .090” in diameter (1/16” or 5/64” drill bit) on your marked points (one hole on each point).

    Drill holes on your marked points with one of the specified drill bits.
    8. Remove all burrs from drilling the lubrication holes. On the inside of the piston, lightly sand with 400-600 grit sand paper. On the outside of the piston, use a ¼” drill bit and twirl it between your fingers over the holes you drilled to break away any edges and imperfections.
    9. Wash the cylinder and piston with soap and water, and use compressed air to remove any water and debris.
    10. Wipe the cylinder wall with light coat of oil. Whichever 2-cycle oil you normally use is fine.
    11. Continue your top end rebuild as normal.
     
    This is how your final product should look all cleaned up and deburred.
    Why doesn't Wiseco pre-drill the holes in the pistons during manufacturing?
    Some Wiseco two-stroke pistons do come with these lubrication holes pre-drilled. However, there are certain applications that use the same piston across a wide range of model years, but the location of the exhaust ports across those years changes. Therefore, while the piston remains the same, the location of the lubrication holes will vary based the specific year cylinder for certain applications.
    Want to see the latest in 2-stroke piston technology? Read about the Wiseco 2-Stroke Racer Elite pistons here.
    See all that Wiseco has to offer for your 2-stroke here.
    Bryan Bosch
    All-new RM-Z250 and DR-Z50 top the list of updated and returning models 

    BREA, CA – July 17, 2018 – (Motor Sports Newswire) –  Led by the advance look at an all-new RM-Z250 motocross machine and the new DR-Z50 mini, Suzuki Motor of America (SMAI) is proud to announce the introduction of its 2019 Motocross, DualSport, Off-road and Youth models including the QuadSport Z90 and QuadSport Z50 ATVs. The completely updated RM-Z250 features a long list of enhancements and performance improvements and now mirrors the cutting-edge styling of its big brother RM-Z450, introduced just last year. For young riders just starting out, Suzuki offers the new DR-Z50 mini. Featuring a host of convenience and safety features, the DR-Z50 is the perfect way to introduce youngsters to the thrill of dirt bike riding.
    All-new from the ground up in 2018, the RM-Z450 returns with key updates to its suspension while Suzuki’s versatile DualSport and DR-Z400SM models continue to provide owners with class-leading performance whether riding on- or off-road. For those ready to take Suzuki’s renowned motocross bike handling to the trails, the RMX450Z returns for serious desert and woods riders. The DR-Z125L is everyone’s favorite trail bike and returns with RM-Z inspired graphics.
    2019 Motocross Models
    Suzuki’s tradition of building championship winning, high performance motocross machines takes the next step forward with the pre-announcement of the all-new, 2019 RM-Z250. Designed to move it to the head of the 250 class, this all-new stunner features a long list of enhancements and performance improvements. Preliminary information on this new motorcycle is available now with full product details and specifications set to be announced in September.
    Evolving the fundamental performance elements of ‘RUN’, ‘TURN’ and ‘STOP’ to a new level, Suzuki has infused the Winning Balance into the new 2019 RM-Z250.
    Suzuki engineers have achieved an even greater level of balance between the race-proven performance of the RM-Z250’s engine and chassis. Particular attention was focused on advancing its ‘TURN’ capabilities to continue Suzuki’s tradition of producing the best handling motorcycles on the racetrack.
    The styling of the RM-Z250 is all-new and unified with that of the RM-Z450.

    NEW 2019 RM-Z250
    New Aluminum Frame & Swingarm More Power and Improved Throttle Response Sleek New Bodywork & Ergonomics New Coil-spring Fork & Shock/Linkage Champion Yellow with Red/Blue Graphics MSRP $TBA Estimated arrival at dealers: February 2019 *Additional information will be available in September 2018
    With a decade’s worth of race win dominance, the 2019 RM-Z450 remains the champion’s choice. Fully-revised in 2018, the RM-Z450 returns with its sleek, race-ready appearance, strong engine and a nimble chassis that continues Suzuki’s tradition of having the best handling 450. To further improve the agile RM-Z450, a new spring has been fitted to the SHOWA BFRC shock with new damping force settings while the coil-spring fork has new damping-force settings as well. Continual improvement is why the RM-Z450 remains the class standard for cornering performance.

    2019 RM-Z450
    DOHC 4-valve, 449cc, 4-stroke Engine Suzuki EFI with Tuning Coupler System Twin-spar Aluminum Frame & Swingarm New Rear Shock Spring Updated Suspension Settings Champion Yellow with Red/Blue Graphics MSRP $8949 Estimated arrival at dealers: August 2018
    2019 RM85
    The Choice of Future Champions Strong & Reliable 84.7cc Two-stroke Engine Six-speed Transmission & Manual Clutch Fully Adjustable SHOWA Suspension Champion Yellow with Red/Blue Graphics MSRP $4199 Estimated arrival at dealers: November 2018
    Enlist in the RM ARMY and enjoy Suzuki Amateur Racing Support!
    Suzuki’s renowned RM Army and Amateur Racing Support continues, offering over $3.8 million in contingency, trackside support, and the opportunity to train with Ricky Carmichael at Suzuki’s exclusive Camp Carmichael. Want to see why champions choose Suzuki? Visit www.racesuzuki.com for more information on Suzuki’s Amateur Support Program and enlist in the RM ARMY!
    2019 DualSport Models
    Suzuki offers the best all-around selection of DualSport models in the industry. As evident with the DR-Z400S, Suzuki DualSport models are fun, reliable and capable motorcycles available to anyone who’s ready to take a ride down an off-road trail or ribbon of asphalt. The versatile DR650S sports the ability to reduce its chassis and seat height for rider comfort and confidence while the DR200S is at home trail riding or commuting; delivering an impressive 88 MPG.

    2019 DR650S
    644cc, Air and Oil-cooled, Four-stroke Engine Push-button Electric Start & Street-legal Lighting Optional Adjustable Seat Height Smooth-shifting 5-speed Transmission Solid Black with Red Graphics MSRP $6599 Estimated arrival at dealers: August 2018
    2019 DR-Z400S
    Liquid-cooled, 398cc DOHC Engine Push-button Electric Start & Street-legal Lighting Slim Chassis with Fully-adjustable Suspension Spoke-style wheels, Aluminum 21” and 18” Rims Solid White Bodywork with Blue/Black Graphics MSRP $6749 Estimated arrival at dealers: November 2018
    2019 DR200S
    199cc OHC, Four-stroke Engine Low 33.3” Seat Height & 278 Ready-to-Ride Pounds Push-button Electric Start & Street-legal Lighting Over 8-inches of Front and Rear Suspension Travel, Solid White Bodywork with Blue/Black Graphics MSRP $4649 Estimated arrival at dealers: August 2018
    2019 Suzuki DR-Z400SM
    Suzuki’s DR-Z400SM combines a narrow, off-road capable chassis with street-legal components to produce a lightweight, Supermotard package that turns, accelerates, and stops better than many sportbikes. The DR-Z400SM has an inverted front fork, wide, spoke-style wheels sporting sportbike tires, and a 300mm floating front brake rotor. There are two color choices for the 2019 DR-Z400SM; Solid White bodywork with red/black graphics plus gold-anodized EXCEL rims on the wheels, or white bodywork with blue/black graphics and blue-anodized rims.
    2019 DR-Z400SM
    Liquid-cooled, 398cc DOHC Engine Push-button Electric Start & Street-legal Lighting Inverted, Fully-adjustable RM-style Fork Solid White Bodywork with Red/Black Graphics with Wide, Spoke-style Wheels with Gold-anodized Rims 120/70-17 & 140/70-17 Sportbike Tires -Or-
    Solid White Bodywork with Blue/Black Graphics with Wide, Spoke-style Wheels with Blue-anodized Rims MSRP $7349 Estimated arrival at dealers: September 2018  
    2019 Off-road Models
    The new 2019 DR-Z50 is a high-quality, Suzuki-built mini-bike that brings ease and convenience to riders just getting started on two wheels. With an automatic clutch, 3-speed transmission, electric starting and a low 22-inch seat height, this RM-styled bike will help build confidence and riding ability for young, supervised riders. The 49cc engine delivers a smooth, controllable power-band plus adult supervisors can adjust the power level so young riders can learn at a proper pace.
    Joining the DR-Z50 is the DR-Z125L that’s ideal for riders of intermediate stature and skill, and the RMX450Z that combines elements of the championship-caliber RM-Z450 with features needed for serious trail work.

    2019 DR-Z50 NEW
    Reliable 49cc, 4-stroke Engine Smooth-shifting 3-speed Transmission & Auto-clutch Push-button electric starting with back-up kick starter Keyed Ignition & Power Limiter for Parental Control Inverted Fork & Single Rear-shock Champion Yellow with Red/Blue Graphics MSRP $1749 Estimated arrival at dealers: September 2018
    2019 DR-Z125L
    Compact & Reliable 124cc 4-stroke Single Smooth-shifting Transmission, Easy-pull Manual Clutch Strong Steel Frame & Beam-style Swingarm Telescopic forks & Single, Link-type Rear Suspension Champion Yellow Bodywork with RM-Z Style Graphics MSRP $3299 Estimated arrival at dealers: August 2018
     
    2019 RMX450Z
    Enduro-ready Off-road Bike based on the RM-Z450 Electric-starting with Kick-start Back-up Competition-ready Instruments and Lighting Black-anodized Wheels with 18-inch Rear Rim Fully-adjustable, SHOWA Fork & Rear Shock Champion Yellow with Red/Blue Graphics MSRP $8999 Estimated arrival at dealers: August 2018  
    Each new Suzuki DualSport, SuperMoto, Off-road, and ATV model is backed by our Limited Warranty1. Additionally the coverage period and other benefits added through Suzuki Extended Protection. Click here to learn more or visit a Suzuki dealer for details.
    1The DR200S, DR650S, DR-Z400S, DR-Z400SM models are covered by Suzuki’s On-road, 12-month Limited Warranty. The DR-Z50, DR-Z125L and RMX450Z models are covered by Suzuki’s Off-road, 6-month Limited Warranty. The QuadSport Z50 and QuadSport Z90 models are covered by Suzuki’s ATV, 12-month Limited Warranty. The competition RM85, RM-Z250 and RM-Z450 models do not have warranty coverage.
    About Suzuki
    Suzuki Motor of America, Inc. (SMAI) distributes Motorcycles, ATVs, Scooters, Outboard Motors and Automotive Parts and Accessories via an extensive dealer network throughout 49 states. Suzuki Motor Corporation (SMC), based in Hamamatsu, Japan, is a diversified worldwide manufacturer of Motorcycles, ATVs, Scooters, Automobiles, Outboard Motors and related products. Founded in 1909 and incorporated in 1920, SMC has business relations with 201 countries/regions. For more information, visit www.suzuki.com
    Suzuki, the “S” logo, and the Suzuki model and product names are Suzuki trademarks or ®.
    Source: Suzuki Motor of America, Inc.

    ronbuell
    Ever been bored or really ticked off by not being able to reach your fuel screw for trailside adjustments?  Well, I decided to do something about it, and not spend a bunch of money to boot!
    Parts liste included:
    Short length of brass tube. Short piece of old, broken speedometer inner cable. Nut from the rejects bin.   I welded the nut to the speedometer cable inner and soldered the other end to the fuel screw using the brass tube as a connector.  I didn't need or fab up a holder for the end, but I wouldn't be too hard. My DIY flexible fuel mixture screw works great and the price is right! I highly recommend this mod.

    Cheap, but effective DIY fuel mixture screw
    Rob@ProX
    Rebuilding a top end is a task most two-stroke owners will run into at one point or another. Here, we go over critical steps and key tips to installing a new piston and ring(s) in your two-stroke.
    Periodically, if you own a two-stroke, there will come a point where you need to rebuild the top end of your engine. Hopefully, this won’t come as a surprise to you and will be part of your planned maintenance schedule versus experiencing an unplanned engine failure. While two-stroke engines are relatively simple mechanical devices, rebuilding them requires knowledge of how they work, attention to detail, and a systematic approach.

    We’re going to cover numerous tips pertinent to two-stroke top end rebuilds. These tips will be discussed chronologically and will encompass all phases of the build from pre-rebuild prep, to disassembly, through post build. The tips we’re going to share shouldn’t be considered inclusive of everything that has to be done, but are tips that focus on things that are either often overlooked or incredibly important. Let’s get started!
    Pre-Teardown
    Diagnosis  - Before tearing the engine apart, are there any signs that a specific problem exists? If so, are there any diagnostic tests such as compression or crankcase leak down that are worth performing?

    Before tearing your engine down, asses the specific problem with you're engine if you're rebuilding due to a running problem.
    Clean Machine - Take time to thoroughly clean the machine before opening up the engine, especially if you will be servicing the top end without removing the engine from the machine.
    Service Manual - Performing engine maintenance without an OEM factory service manual is not recommended. Make sure you have a manual for your machine prior to starting work. The manual is the only place you’ll find service limits, torque specs, and other key data.
    Disassembly
    Limit Contaminants - Once the cylinder has been removed wrap a clean, lint-free rag around the top of the crankcase. Dirt is one of the leading causes of engine wear, and limiting the opportunity for dirt to enter the crankcase is very important.

    Keep a lint-free rag at the top of the crankcase at all times while it is open and exposed to potential contaminants.
    Piston Removal - Easy piston circlip removal can be accomplished by using a pick and needle nose pliers. Insert the pick into the dimple in the piston and behind the circlip. Then use it as a lever and pry the circlip out partially. Once out partially, grab the circlip with needle nose pliers. During this process, be careful not to scratch or mar the wrist pin bore as this will make removing the wrist pin much more difficult.

    Use tools as needed to aid in circlip removal, but be careful not to mar the pin bore so the wrist pin can be easily removed.
    The ease of pin removal will be largely dependent on the engine design and condition of the bore. If the pin can be removed by hand, great, if not, light tapping while supporting the rod is permissible. Otherwise, a pin puller should be utilized which can be bought or made. In its simplest form, this can consist of an appropriately sized bolt, nut, and socket. Once the wrist pin has been removed, the piston can be removed from the rod.

    Hopefully, the wrist pin can be removed by hand once the circlip is out. If not, an appropriately sized socket with some light tapping from the opposite end can help break it loose.
    Power Valve Disassembly - Prior to taking the power valve system apart, spend some time reviewing the procedure in your service manual. For additional insight into how the components interact, review the exploded views in the service manual and look at part microfiches, which can be found online.

    Online microfiches can be very helpful to double-check reassembly of the power valve. They can be found on many motorcycle dealer websites.
    When removing the power valve system, consider laying the components out on a clean rag in an orientation that correlates to how they are installed in the engine. This is a relatively simple thing to do that will help you remember how they are installed later. When it comes to cleaning the components, clean them one at a time or in small batches so that they don’t get mixed up.

    Lay out all the parts of your power valve assembly as you disassemble it. This will help you keep everything organized, and make sure you get it back together correctly.
    Inspection
    Reed Valve - Don’t forget to check the condition of the reed valve petals, cage, and any stopper plates. Most service manuals will detail the acceptable clearance between the petal tips and cage as well as the stopper plate height. Ensure any rubber coatings on the reed cage are in good condition.

    Inspect all reed valves components thoroughly before reassembling the top end. Any parts showing signs of excessive wear or damage should be replaced.
    Intake Manifold - Check the intake manifold for cracks. Cracks are more common on older engines, and propagation all the way through the manifold can lead to air leaks.
    Exhaust Flange - Check the condition of the exhaust flange and ensure that it is not excessively worn. An excessively worn flange will make exhaust gas sealing difficult, hamper performance, and leak the infamous spooge. 
    Power Valve Components - Take a moment to review the condition of all the power valve components. Significant wear can occur over time and lead to performance losses.
    Rod Small End - Check the small end rod bore for surface defects such as pitting, scratches, and marring. Any severe defects in the bore will necessitate rod replacement.

    The rod small end is a critical point of inspection. Any damage to the inside surface could affect the small end bearing, leading to a chain of top end problems and potential failure.
    Sourcing New Components
    When freshening up the top end in your two-stroke, it’s important to reassemble with quality components. A deglazed and honed or bored and replated cylinder is a critical component to ensuring reliable performance from your new top end. Your local cylinder shop should be able to handle the bore and replate when necessary, and a simple deglazing can be accomplished with a Scotch-Brite pad. Be sure to retain the 45-degree honing mark angle.
    There are a lot of choices for new pistons from the aftermarket out there, but many people choose to stick to OEM. However, when ordering from the OEM, every individual part must be ordered separately, including the piston, ring, pin, clips, gaskets, etc. Dealing with all these part numbers and chancing forgetting a component can be a pain, and get expensive.

    ProX two-stroke pistons are manufactured by OEM suppliers, and come with the piston, pin, ring(s), and circlips all under one part number.
    ProX two-stroke pistons are manufactured by the same OEM-suppliers to exact OE specs. They are available in A, B, C, and D sizing for most applications. ProX pistons come with the piston, ring(s), pin, and clips all in one box. Complete top-end gasket kits can even be ordered under one part number. ProX pistons provide an OEM-replacement option with less hassle and less strain on your wallet.
    Find ProX pistons for your bike here.

    Even though ProX pistons are made by OE suppliers, the quality control difference is evident. On the left is a ProX piston for a Honda CR250, and on the right is a brand new piston out of the box from Honda. Which would you choose?
    Measurements
    The number of measurements that should be taken throughout the top end rebuild will be discretionary. At ProX, we strive for excellence and err on the side of caution when it comes to engine building, so our builds consist of numerous measurements and inspections prior to reassembly. For us, this ensures a high level of confidence and safeguards against external oversights. We recommend the same to anyone building an engine.
    Below is a list of measurements that we routinely make when rebuilding a two-stroke top end:
     Piston ring end gaps  Piston-to-cylinder clearance  Rod small end diameter Out of these measurements, confirming or adjusting the ring end gaps is by far the most important, followed closely by ensuring the cylinder bore is within spec with respect to diameter, straightness, and roundness. Understandably, some measurements may be difficult for the average home builder to execute, usually due to not having the right equipment, however, a competent shop should be able to assist.
    Ring end gaps can be checked by installing the ring in the bore without the piston, and using a feeler gauge to find the measurement. Correct ring end gap is listed in the installation instructions that come with a new ProX piston.

    ProX rings often do not need to be filed as they are pre-gapped, but it's always a good idea to make sure your end gap is within the provided spec.
    Piston-to-cylinder is another measurement that should be checked before final assembly. For this, use a bore guage and a set of calipers to measure the bore size. Next, grab a set of micrometers and measure the piston. ProX pistons should be measured perpendicular to the wrist pin, a quarter of the way up the piston skirt from the bottom. Subtract your piston size measurement from your bore size, and you have your piston-to-cylinder clearance. ProX pistons come with a chart on the instruction sheet that shows the range your clearance should be in.
      
    Measuring piston-to-cylinder clearance is a smart precaution to help ensure you won't run into any unexpected issues with your new top end.
    A final measurement we recommend taking is the rod small end diameter. This is important because sometimes these can get worn out and create free play for the small end bearing, resulting in damage to the bearing and most likely the entire top end. It can be done using the same method as the bore diameter. Compare your measurement to the acceptable range in your owner's manual.

    Making sure the diameter of the small end of the rod is within spec is often overlooked, but can prevent a serious top end failure.
    Prep Work
    Cylinder Cleaning - Once the cylinder has been deglazed or has come back from replating, it should be cleaned one final time. There is almost always leftover honing grit that will need to be removed. To effectively clean the cylinder, use warm soapy water and a bristle brush, followed by automatic transmission fluid or a similar cleaning solution and a brush or lint-free rag. To check the cleanliness of the cylinder, rub a cotton swab around the bore and look for contaminants. Clean the bore until no contaminants are visible on the cotton swab. Any honing grit that remains in the cylinder will facilitate premature wear of the piston rings.

    A clean, de-glazed, and properly honed cylinder is key to piston and ring function and longevity.
    Power Valve Function - Cylinders that have been exchanged or replated should have the power valve system reinstalled ahead of final installation. Often times, excess plating can inhibit power valve movement. To correct this, the excess plating must be carefully removed. On cylinders utilizing blade style power valves, the blade position with respect to the cylinder bore should be checked to ensure the blade does not protrude into the bore.

    Assemble the power valve before installing the new piston and reinstalling the cylinder. Be sure to check that the power valve is moving as it should, and not protruding into the bore.
    Piston - It is usually easiest to prepare the new piston as much as possible by installing one of the circlips and the ring pack ahead of joining it to the connecting rod. Unless your service manual dictates which circlip must be installed first, choose the easiest installation orientation. Typically, your dominant hand and preferred work orientation will dictate which side you choose to install the circlip on.
     
    It's easier to install one clip and the piston ring(s) before fixing the new piston to the connecting rod.
    Reference your service manual to determine the correct orientation of the circlip. Usually, the open end of the circlip should be oriented to the 12 or 6 o’clock position. Temporarily install the wrist pin and use it as a backstop so that the circlip is forced to move into its groove. Installing the circlip should be done by hand to limit the chance of deformation. Orient the circlip to the desired position, then push the open ends of the circlip into position first. Be careful not to scratch or mar the wrist pin bore in the process! Once installed, use a pick or screwdriver to confirm the circlip is fully seated and does not rotate. Any circlips that can be rotated must be replaced because they have been compromised and deformed during installation.

    Make sure to note the orientation of each clip after installation. Some manuals may recommend specific positions depending on the piston, but always be sure the gap is not lined up with or near the dimple(s).
    Rings - The compression ring(s) will be directional, and the top of the ring is typically denoted by markings near the end gaps. Apply a thin coat of oil to the ring, then carefully work the ring into position, making sure to line up the ring end gaps with the locating pin in each ring groove.

    Install the ring(s) with the marking(s) facing up, and make sure the ring end gap is lined up with the locating pin in the ring groove.
    Installation
    Piston - On the top of the piston, an arrow will be imprinted, which typically denotes the exhaust side of the piston. Consult your service manual to confirm the proper orientation of the arrow and piston. Apply a light amount of assembly lube to the small end bearing and wrist pin bore on the piston, then install the bearing. Align the piston with the small end of the rod, and slide the wrist pin into place. Once again, use the wrist pin as a backstop, then install the remaining circlip into position. Use a pick or screwdriver to confirm it is fully seated and does not rotate.

     Don't forget to apply some assembly lube to the ring and piston skirts before assembly!
    Cylinder to Piston - In most applications, a ring compressor is not required to compress the rings and install the piston into the cylinder. Lightly oil the cylinder bore with assembly lube or engine oil, then lube the piston skirt and ring faces. Prior to installing the piston and rings, confirm one final time that the piston ring ends are oriented correctly to their respective locating pins.
     
    Once the new piston is installed on the connecting rod, apply some assembly lube to the cylinder wall, and carefully slide the cylinder over the piston. Squeeze the ring with your hand as you slide the cylinder on, simultaneously making sure the ring end gap remains aligned with the locating pin.
    Position the piston at or near TDC then carefully lower the cylinder bore down onto the piston. Use your fingers to compress the ring(s) and ensure the cylinder bore is square to the piston. Feel how easily the cylinder slides over the piston and rings. The installation of the cylinder should be smooth and offer little resistance. If resistance is felt, stop immediately and assess the ring pack. Occasionally one of the rings may come out of position in its groove and snag the cylinder bore. This typically happens as the ring transitions out of your fingers and into the cylinder bore.
     
    Once the cylinder is safely over the ring, slide it all the way on keeping the piston at top dead center (TDC). Don't forget to torque your cylinder and head nuts to the specification listed in your manual.
    Post Build
    Torquing - Your cylinder and head nuts should always be torqued to the specifications outlined in your service manual. Double check all the nuts are set at their corresponding specs.

    Spark Plug - Don’t forget to install a new spark plug and if necessary gap it appropriately.
    Air Filter - Be sure to install a clean air filter prior to start up.
    Crankcase Leak Down Test - As one final precautionary measure perform a crankcase leak down test. A crankcase leak down test will help confirm all the seals, gaskets, and joints are sealing as they should.
    Break-In - When running your new top end for the first time, keep the engine slightly above idle, with slow and mild revs until the engine starts to get too hot to touch. Then, shut the engine off and let it cool until it is warm to the touch. Repeat this process, revving slightly higher and letting the engine get partially hotter each time. After 3 cycles like this, let the engine completely cool, then check all your fluids and re-check the torque on your cylinder and head bolts.
    Once that is squared away, you can begin break-in runs riding the bike. Make sure to keep the RPMs varied while riding for the first time, not letting the engine lug or sit at idle. A safe bet would be to ride the bike like this for 5 minutes, then 10 minutes, and finally 15 minutes, with adequate cooling in between. This will ensure your piston ring(s) are evenly and properly broken in. It’s never a bad idea to double check your fluids and torque one more time after complete cool down.

    Bryan Bosch
    Engineering, development, engine production and vehicle assembly into one location and will increase efficiency. Nearly 700,000 square foot facility on a site covering more than 40 acres. This all new facility will produce the majority of Suzuki two-wheeled products for U.S. distribution.  
    New Facility Merges Three Separate Facilities and Positions Suzuki for Continued Growth
    BREA, CA – June 26, 2018 – (Motor Sports Newswire) –  Suzuki Motor of America, Inc (SMAI), is happy to announce the creation of a new manufacturing plant in Hamamatsu, Japan, home to its parent company, Suzuki Motor Corp. (SMC). The new facility will combine engineering, development, engine production and vehicle assembly into one location and will increase efficiency in the production and delivery of Suzuki’s ever-diversifying motorcycles..
    Originally announced in 2014, this five-year consolidation plan is near completion. Previously, Suzuki motorcycles were developed and manufactured across three locations in Japan – product engineering and development teams worked at the company’s Ryuyo facility; Suzuki produced engines at its Takatsuka plant; and motorcycle assembly lines operated at its Toyokawa plant. These three operations will now be centralized into the new Hamamatsu Plant in the Miyakoda district, in a nearly 700,000 square foot facility on a site covering more than 40 acres.
    This all new facility will produce the majority of Suzuki two-wheeled products for U.S. distribution. The site of the facility was chosen in part due to its geographically desirable location and proximity to Suzuki headquarters.
    Suzuki also operates an All-Terrain Vehicle assembly plant in Rome, Georgia.  Active since 2001, Suzuki Manufacturing of America (SMAC) exclusively builds Suzuki’s award-winning line of utility-focused ATVs for worldwide distribution. Suzuki launched all-new versions of its KingQuad 750 and KingQuad 500 in May.
    Source: Suzuki Motor of America, Inc.

    Kevin from Wiseco
    When it comes to overall strength, there's no beating a forged piston. But what is the process that yields the toughest parts in the racing world? We'll show you. 
    When it comes to turning raw metal alloys into useful things, two processes dominate - casting and forging. Both have their place, but when strength and light weight are priorities, forging is the method of choice. Though it’s been around for more than six millennia, forging processes continue to advance the state of the art, bringing us everything from sharper, more durable kitchen knives to more fuel efficient jet engines, plus things much closer to our heart: lighter, stronger pistons.

    Although forging is a metalworking process thousands of years old, it’s still the best method to produce components with the highest strength and durability.
    Forging is defined as the controlled deformation of metal into a desired shape by compressive force. At its most basic, it’s a blacksmith working a piece with a hammer and anvil, and those first metalworkers toiling at their forges discovered something important about the pieces they were crafting – compared to similar objects made from melted and cast metal, they were stronger and more durable.
    Though they knew the finished product was superior, what those ancient smiths didn’t suspect was that the act of forging was changing the internal grain structure of the metal, aligning it to the direction of force being applied, and making it stronger, more ductile, and giving it higher resistance to impact and fatigue. While a cast metal part will have a homogeneous, random grain structure, forging can intentionally direct that structure in ways that give a finished part the highest structural integrity of any metalworking process. 
     
    Wiseco forged pistons start as raw bar stock in certified 2618 or 4032 aluminum alloy. Once they’re cut into precisely-sized ‘pucks’ they’re ready to be preheated in preparation for forging.
    Although many performance enthusiasts might put billet parts at the top of the heap in terms of desirability, the reality is that the billet they are created from doesn't have the same grain properties of a forging. 

    The Wiseco Forging Process
    Today’s state of the art in forging technology is far removed from the smith’s bellows-stoked fire and anvil. In Wiseco’s ISO 9000-certified forging facility, pistons begin life as certified grade aluminum bar stock, cut to precise lengths to form slugs. The choice of material is critical - conventional wisdom has always said that a forged piston requires additional piston-to-bore clearance to allow for expansion, leading to noise from piston slap until the engine gets up to temperature, but per Wiseco’s Research and Development Manager David Fussner, “Forged pistons do require additional room temperature clearance. However, the 4032 forging alloy we use has about 12% silicon content, and this significantly controls the expansion to nearly the same as a 12% silicon cast piston. The 2618 alloy expands a bit more and does require a bit more room temperature clearance than 4032.”

    Pistons are forged in a ‘backwards extrusion’ process where a moving punch presses the raw material into the die to form the rough shape. The process takes only a fraction of a second (longer in the isothermal press), and the speed of the press helps determine how material flows, and therefore the internal grain structure of the forging.
    While 4032 is more dimensionally stable across the typical operating temperature range seen inside an engine, it does give up a small advantage in ductility to 2618, which has a silicon content of less than 0.2 percent. This makes 2618 a better choice for applications where detonation may be an issue, like race engines running high boost or large doses of nitrous oxide. The low silicon alloy’s more forgiving nature in these instances makes up for the tradeoffs in increased wear and shorter service life compared to 4032.
    Once cut to the proper size, slugs are heated to a predetermined temperature and moved to the forging press itself, which is also maintained at a controlled temperature. There are two different types of presses employed at Wiseco; mechanical and hydraulic. Both have a long history in manufacturing, and each has specific strengths. Mechanical forging presses are well-suited to high production rates, helping to keep the overall cost of high-quality forged components affordable. Hydraulic presses have the advantage of variable speed and force throughout the process, allowing greater control of material flow, which can be used to produced forged components with even more precisely controlled physical properties.

    Wiseco’s isothermal hydraulic press forging machines use precise digital control of the temperature of the raw material, the punch, and the die, as well as the pressure exerted during the full motion of the forge. This allows very close control over the physical properties of the finished forging.
    Regardless of the type of press, pistons are forged using a “backwards extrusion” process where the material from the slug flows back and around the descending punch to form the cup-shaped forging. Picture the stationary part of the press (the die) as the mirror image of the piston top, and the punch as the mirror image of the underside. As the punch descends, the puck is transformed into the rough piston shape with material flowing up along the sides of the die and punch to form the skirt. This entire process takes place on the scale of milliseconds (on the mechanical press), and the all-important flow stresses of the material are determined by the strain rate (or speed) and load applied by the press.
    In addition to three mechanical forge presses, Wiseco also has two isothermal hydraulic presses in-house. These state of the art forges maintain the temperature of the piston slug, the die, and the punch very accurately through computer control, delivering more precise dimensions and geometry for the finished pieces, as well as allowing for more complex designs to be successfully forged, and even the creation of metal matrix composite forgings.

    Once the puck (left) has been transformed into a forged blank (middle), it still has a ways to go before becoming a completed piston (right).
    The Heat Is On
    Once the forging process is complete, the components next move to heat treatment. Wiseco’s aerospace-grade heat treatment facility is located in the same plant as the presses, and here the pistons go through a carefully controlled process of heating and cooling that relieves stress induced during forging, increases the overall strength and ductility of the metal, and provides the desired surface hardness characteristics. 
    While casting can deliver parts straight out of the mold that are very close to their final shape, forgings require a bit more attention in order to get them into shape. Fussner explains, “In a dedicated forging for a specific purpose, the interior of the forging blank is at near-net as it comes off the forging press.  And in some cases, we also forge the dome near-net with valve pockets and some other features. Other than these items, most other features do require machining.”

    Pistons aren't the only thing Wiseco forges and machines in-house. Wiseco clutch are also forged and machined, as well as finished with hard anodizing. The forging (left) allows the basket to closer to the final shape before machining. The basket shown here is just post-machining.
    One basic forging may serve as the starting point for many different types of finished pistons, unlike castings which are typically unique to a single design or a small group of very similar designs. Regardless of the manufacturing method for the piston blank, some degree of final machining needs to take place to create a finished part. “As a ballpark percentage, I would say about 75% of the forging blank would require machining.” Cast pistons also require finish work on the CNC machine, but this is almost always less extensive than a similar forged piston. “That’s the main reason why forged pistons are more expensive than a cast piston,” Fussner adds. 
    Another reason for the added expense of forging is the significant cost of the initial tooling for the die and punch, which must be made to exact specifications and be durable enough to survive countless forging press cycles. Per Fussner, “We control these costs by making all our forging tooling in house at Wiseco headquarters in Mentor, Ohio.” The ability to make their own tooling, doing their own forging, and their in-house heat treatment facilities make Wiseco the only aftermarket forged piston manufacturer in the United States with these unique capabilities.
    Once the machining process is complete, Wiseco pistons can also receive a number of different proprietary coatings to fine-tune their performance. These include thermal barriers as well as wear reduction treatments.
    Though forging is a technique literally as old as the Iron Age, it’s still the undisputed king of manufacturing techniques for light, strong, durable components. Wiseco continues to refine the process with the latest methods, materials, heat treatment, and machining to provide the highest quality aftermarket components available, at an affordable price.

    Wiseco forged pistons provide superior quality and performance at an affordable price thanks to the company’s close control over every step of the manufacturing process.
    Bryan Bosch
    FOR IMMEDIATE RELEASE
    Honda Broadens CRF Lineup with Expansive New-Model Launch
    Largest performance off-road release yet includes new models for diverse applications

    IRVINE, Calif. (May 23, 2018) – During a recent “CRF Collective” unveiling ceremony at Fox Racing headquarters, Honda announced its most far-reaching range of performance off-road models ever, expanding the group by three and significantly improving the four returning models. Leveraging the brand’s unparalleled experience in the manufacture of dirt bikes, Honda’s performance off-road lineup now includes CRF machines for riding applications including motocross, closed-course off-road, pure off-road, and even dual sport.

    All seven models are based on the platforms of Honda’s revolutionary motocrossers, the CRF450R and CRF250R. Those two machines return for 2019 but with important updates, as does the closed-course off-road CRF450RX. In addition, Honda is offering a factory-replica version of its full-size motocrosser called the CRF450RWE (“Works Edition”). The trail-ready CRF450X is entirely new for 2019, and it’s joined by a road legal CRF450L that enables customers to connect trails via asphalt. Finally, Honda is also introducing an all-new CRF250RX closed-course off-road machine.
     

     
    CRF450L Dual Sport
    The trails are calling, and the all-new road-legal CRF450L answers, expanding customers’ off-road possibilities by enabling access to the best riding trails, even when that means connecting them via asphalt roads. Street legality is achieved via features like LED lighting, mirrors, and a dedicated exhaust system. Equally at home in the woods or desert, the CRF450L has a wide-ratio six-speed transmission for maximum adaptability, while a lightweight, 2.0-gallon tank offers great range. Compared to the CRF450R motocrosser, crank mass is up for tractability in technical conditions, where a large-capacity radiator keeps things cool.
    Color: Red Target Price: $10,399 Availability: September Info: https://powersports.honda.com/2019/crf450L.aspx >>> More pictures, video, specs & discussion on the 2019 Honda CRF450L <<<


     
    CRF450RWE (Works Edition)
    For the 2019 model year, you don’t have to be Ken Roczen to enjoy a CRF450R with factory enhancements, as the new CRF450RWE features a number of upgrades based on the bikes in the Team Honda HRC race shop. Rocketing to the top step of the podium through the use of a specially designed cylinder head with hand-polished ports, Yoshimura titanium slip-on muffler, and special ECU settings, this new model offers increased low- and mid-range torque. It also features the same graphics as Roczen’s No. 94 race bike, including a Throttle Jockey factory seat cover. Upgraded black D.I.D LT-X rims are included, along with black triple clamps and a gold RK chain. Titanium nitride-coated fork legs and an updated, titanium nitride-coated shock shaft increase traction and bump absorption.
    Color: Red Price: $11,499 Availability: August Info: https://powersports.honda.com/2019/crf450r.aspx

     
    CRF450R
    Already the industry’s top-selling motocrosser and the winner of the 2018 Daytona Supercross at the hands of MotoConcept’s Justin Brayton, the CRF450R receives a number of important updates for 2019. Better engine performance is achieved through a new combustion-chamber shape, as well as improved over-rev characteristics through a refined oil-management system. The frame and swingarm have been revised for optimized rigidity and weight reduction, while the braking system has been updated with a lightweight front brake caliper featuring a large-piston design. As a result of the weightsaving measures, the CRF450R is 1.76 lbs. lighter than its predecessor. For added performance and increased comfort, the 2019 model features new ECU settings, HRC launch control, a Renthal Fatbar® handlebar and adjustable handlebar position. Black rims and redesigned fork protectors are also new. This is how you convert the “Absolute Holeshot” into moto wins.
    Color: Red Price: $9,299 Availability: August Info: https://powersports.honda.com/2019/crf450r.aspx

     
    CRF450X
    Having featured heavily in Honda-mounted teams winning 20 of the last 21 Baja 1000s, the CRF450X gets a complete overhaul for 2019, based on the modern CRF platform but with off-road-appropriate features. A true off-road machine that’s ready for racing or trail riding, this model features a headlight, taillight, and side stand, as well as an 18” rear wheel and lightweight 2.0-gallon fuel tank. For maximum versatility in challenging terrain, the CRF450X also features a 49mm Showa fork with dedicated settings, wideratio six-speed transmission, and higher crank mass than the CRF450R.
    Color: Red Target Price: $9,799 Availability: October Info: https://powersports.honda.com/2019/crf450X.aspx

     
    CRF450RX
    Currently campaigned by JCR Honda’s Trevor Bollinger and Trevor Stewart in GNCC and WORCS competition, respectively, the CRF450RX inherits the same performanceenhancing features of the 2019 CRF450R, including an updated cylinder head and refined oil-management system, while still featuring off-road-specific features like a 2.2gallon resin fuel tank, 18-inch rear wheel, and aluminum side stand. Suspension is specially tailored to the CRF450RX and uses low-friction fork oil. For added performance and increased comfort, the 2019 model features new ECU settings, HRC launch control, a Renthal Fatbar handlebar, and adjustable handlebar position. Black rims and redesigned fork protectors are also new.
    Color: Red Price: $9,599 Availability: September Info: https://powersports.honda.com/2019/crf450rx.aspx

    CRF250RX
    Based on Honda’s successful 250cc motocrosser, the all-new CRF250RX joins the CRF450RX as a weapon for closed-course off-road competitions throughout America. Equipped with a larger-capacity, 2.2-gallon resin fuel tank, 18-inch rear wheel, and aluminum side stand, the RX makes quick work of challenging situations, its dedicated suspension and ECU settings helping the rider work through even the toughest trail sections. As with the CRF250R, HRC launch control, a Renthal Fatbar handlebar, and black rims are standard.
     
    Color: Red Target Price: $8,299 Availability: September Info: https://powersports.honda.com/2019/crf250rx.aspx

     
    CRF250R
    Newly introduced in 2018, the CRF250R has seen the GEICO Honda and TiLube Honda teams earn multiple wins in AMA Supercross and Arenacross competition, respectively, while also achieving success in amateur national races. For 2019, the model is revised with increased low-to-midrange engine performance for improved corner exiting. Inspired by the factory version, the Double Overhead Cam engine features updated cam profiles
    and intake- and exhaust-port profiles, a 50mm shorter right exhaust pipe, and a 2mm smaller throttle body. Riders can select from three engine modes for ideal performance depending on conditions, while HRC launch control has been adopted for improved race-start performance. A Renthal Fatbar handlebar sits in a four-position-adjustable top clamp, while the braking system has been updated with a lighter, CRF450R-inspired caliper with larger piston for optimum braking performance. Black rims are standard.
    Color: Red Target Price: $7,999 Availability: September Info: https://powersports.honda.com/2019/crf250r.aspx

     
    CRF150R / CRF150RB
    Raced by Amsoil Honda hotshot Hunter Yoder on the amateur national circuit, Honda’s smallest motocross machine returns for 2019, featuring a Unicam four-stroke engine thatoffers a spread of ample, useable power and torque across the rev range. Suspension duties are handled by Showa, with a 37mm inverted fork and Pro-Link rear link system. In addition to the standard version, Honda offers the CRF150RB, which features larger
    wheels, a taller seat, a longer swingarm, and more rear-suspension travel.
    Color: Red Target Price o CRF150R: $5,099 o CRF150RB: $5,399 Availability: August Info: http://powersports.honda.com/2019/crf150r.aspx
     
    ABOUT AMERICAN HONDA
    American Honda Motor Co., Inc., is the sole distributor of Honda motorcycles, scooters, ATVs and Side-by-Sides in the U.S. American Honda’s Motorcycle Division conducts thesales, marketing and operational activities for these products through independent authorized Honda retail dealers. For more information on Honda products, go to powersports.honda.com.
    Bryan Bosch
    Featuring Key Upgrades Husqvarna 2019 Enduro Motorcycles Again Set The Benchmark for Quality, Technology & Performance
     
    May 17, 2018 – (Motor Sports Newswire) – Husqvarna Motorcycles are proud to lift the covers off their complete range of 2019 enduro models – a sophisticated line-up of premium machines that perfectly embody the brand’s pioneering spirit and feature the most advanced technology ever seen in the offroad motorcycles segment.
    Husqvarna Enduro TE 250i MY19
    The whole range features state-of-the-art, powerful and light engines, together with the most advanced engine management systems. With innovative, recently introduced electronic fuel injection on the 2-stroke TE 250i and TE 300i models, all 4-stroke machines benefit from traction control with electric starters fitted as standard on all models apart the TX 125.
    Husqvarna Enduro TE 300i MY19
    For model year 2019 Husqvarna Motorcycles introduce a list of carefully-considered updates across their enduro line-up. Combining top-level performance with unprecedented ease of use across all terrains, the 2019 enduro models are here to deliver a next-level enduro riding experience.
    KEY FEATURES ACROSS THE RANGE

    For model year 2019 Husqvarna unveil an exciting new generation of seven [eight with the TE 150 for the US market] new 2-stroke and 4-stroke enduro machines.
    Husqvarna Enduro TX 125 MY19
    Remaining true to their commitment to never-ending development, for MY19 Husqvarna Motorcycles’ engineers introduce a new series of settings for both the WP Xplor 48 forks and the WP DCC shock. The latest suspension on all Husqvarna enduro models provides advanced damping characteristics with a stiffer setting for more bottoming resistance, to suit the needs of a wide range of offroad riders.
    Husqvarna Enduro FE 250 MY19
    Updates for MY19 include the new Diaphragm Steel Clutch on the TX 125 and TE 150 and the new clutch cover with improved wear resistance on all models.
    Husqvarna Enduro FE 350 MY19
    Retaining their dynamic, sharp and sleek looking bodywork, Husqvarna’s 2019 enduro models feature a futuristic design in their brand new graphics, which stylishly acknowledges the brand’s Swedish heritage. Coinciding with the unveiling of the enduro range, Husqvarna Motorcycles are pleased to introduce a new line-up of clothing and accessories.
    Husqvarna Enduro FE 450 MY19
    Combining Swedish inspired design with premium quality, the 2019 clothing range offers casual and functional garments to meet the needs of all dedicated fans. Enriched for 2019, Husqvarna Motorcycles’ range of accessories contains premium parts designed to enhance and protect all enduro machines.
    Husqvarna Enduro FE 501 MY19
    The new Husqvarna Motorcycles MY19 enduro range will be available in Europe from May 2018 onwards, at all authorised Husqvarna Motorcycles dealers.
    For all details on pricing and availability, please refer to your national Husqvarna Motorcycles subsidiary or importer. Media Partners,
    The full Media Kit is available for download here:
    http://bit.ly/HQV_ENDURO_MY19_MEDIA_INFORMATION
     
    Husqvarna Motorcycles. Tradition on two wheels since 1903.
    Husqvarna Motorcycles are widely known and respected in the off-road world for a heritage of competition and numerous motocross and enduro world championships. Originally founded in Sweden in 1903, Husqvarna Motorcycles have been designed and manufactured in Mattighofen, Austria since 2013.
    Source: Husqvarna Motorcycles GmbH

    Rob@ProX
    We have a used 2006 YZ450F that we're rebuilding step-by-step, and documenting along the way. In this part 1 feature, we'll go over how to replace a 4-stroke piston. Click here to watch the quick tip video to go along with it!
    The top end in a four-stroke can be split up into two major sections: the head, and the cylinder and piston. They both require specific attention and critical steps to ensure proper opertation once everything is back together.
    We replaced the worn stock piston with an OEM quality forged ProX piston kit. It includes the rings, wrist pin, circlips, and installation instructions. The pistons are available in A, B, and C sizes, to accomodate for the size of your cylinder as it wears.
     
    Our new ProX forged piston compared to the stock, used piston. Carbon deposits on the crown are common after running hours, but can decrease power and efficiency.
    Disassembly
    To prepare to disassemble your head and cylinder, you'll need to remove the seat, gas tank, exhaust system, and carburetor (or throttle body). While not always required, removing the sub-frame, shock, and air boot make accessibility to the engine a lot easier in most cases.
    Once those major components are removed, you'll need to remove any other components attached to the head or cylinder, such as clutch cable guides, spark plug boots, and electrical connections.
     
    Removing the subframe, airboot, and shock, in addition to the other components, provides much better access to all sides of the motor. Don't forget to remove any cable guides or other items bolted to the head/cylinder.
    Next, remove the cam cover, loosening the bolts incrementally until they are all loose. With that off, it is best to make sure your camshafts are not fully compressing any of the valve springs before you loosen the cam caps. You can do this by slowly rotating the crankshaft via the kickstarter. With the cam caps removed, loosen and remove the cam chain tensioner next. This will give you the slack to remove the timing chain completely. You can now lift the camshafts completely out, handling carefully.
    Now you can loosen the head bolts in incrementally in a crossing pattern. Remove the head and place it aside, handling it carefully. Next, do the same for the cylinder bolts, and carefully remove the cylinder. As you remove the cylinder, the piston is going to stay on the connecting rod, so it helps to hold the connecting rod steady as you wiggle the cylinder off the piston. It is always a good idea to fill the opening of the cases with a lint free rag to prevent debris or loose parts from falling in.

    Remove the cam cover and head bolts incrementally until loose. This prevents the chance of warping.
     
    Finally, you can remove one wire lock from the stock piston using a pick or small screwdriver. Slide the wrist pin out, and remove the piston from the small end of the connecting rod. Be very careful no to drop anything into the cases during this step, and throughout the entire process.
    Cleaning
    With everyting removed, you'll need to clean any old gasket material and other residue off your sealing surfaces. This includes the base for the cylinder on the cases, top and bottom surfaces of the cylinder itself, and the bottom surface of the head that seals to the cylinder.
    For large or difficult pieces of material, it is common to use a razor blade for removal. However, be gentle and careful not to put deep grooves or scratches in the surfaces. Also, don't cut your finger open, or off.

    Scrape old gasket material off carefully, being cautious of any grooves or scratches in sealing surfaces and personal injury.
     
    Final cleaning commonly consists of using carb cleaner, or a similar chemical cleaner, and a rag to achieve completely clean and flat surfaces.
    Cylinder Prep
    Before you go and put that cylinder back in with your new piston, you'll want to inspect it for signs of wear, and measure it to make sure it's within spec (refer to your owner's manual for proper specifications). If there is minimal glazing on the cylinder, no grooves worn in, and it's within spec, you should be ready to reinstall after a good honing. Always use a diamond tipped honing brush for resurfacing work. If you're unsure about performing any cylinder prep work yourself, talk to your local dealer about cylinder shops, where any prep work required can be performed.
    ProX pistons are available in multiple sizes to accomodate for cylinder wear, so be sure your bore measurements correlate with the size of piston you're installing.

    Make sure your cylinder is the correct bore size for your piston, and properly cleaned and honed, as pictured here.
    Reassembly
    When you have your cylinder prepped and ready, now is a good time to double check your piston-to-wall clearance and ring end gap. For piston-to-wall, measure the size of your ProX piston using a micrometer only. Measure the piston on the skirt, 90 degrees from the wrist pin bore, at the point on the skirt that is 1/4 of height of the piston from the bottom. Refer to your manual for acceptable piston-to-wall clearance range. When measuring ring end gap, install the top ring and second ring (seperately, and if applicable) approximately 1/4" into the bore. Use a feeler gauge to be sure ring end gap is within the dimensions specified in your piston kit instructions. ProX rings are pre-gapped, but it is always good practice to double check.

    While ProX rings are pre-gapped, it's still a good idea to double check your ring end gap.
    Install the rings in the proper order and location on your pistons. Refer to the instructions that come with ProX piston kits to be sure you are installing the rings in the correct fashion and location. After this, install one wire lock into your piston, being sure it is properly seated.
    Click here for our tips on installing wire locks.
    Use your finger to put a layer of motor oil on the cylinder wall. Next, put a layer of oil on the outside of your new piston (on the outside of the rings, on the ring belt, and on the skirts). You don't want your new piston and rings breaking in under dry conditions. Use the normal motor oil you use in your 4-stroke.
    Piston installation can be done via more than one method, but in our case, we installed the piston in the cylinder before attaching it to the connecting rod. Either way, be sure your piston is facing the correct direction, meaning the exhaust valve reliefs line up with the exhaust side of the head. There will be markings on the crown of ProX pistons to indiciate which side is the exhaust side. Also, make sure your rings remain in the proper location as you slide the piston into the cylinder. 

    The arrow shows the marking on the piston crown that indicates that is the side of piston that needs to face the exhaust.

    Before installing the new base gasket, piston and re-installing the cylinder, make sure the surface is clean and the crankcase is free of debris. While the top end is off, this could also be a good time to make sure your crankshaft is in spec.
    Next, lay your new base gasket on the cases, lining it up properly. Install the piston (which should remain in the cylinder) onto the connecting rod by lining up the pin bore with the small end bore, and sliding your new wrist pin (put a layer of oil on this before installing) completely through, until it stops against the one wire lock previosuly installed. With the piston secured to the connecting rod via the wrist pin, install your remaining wire lock, and make sure it is properly seated. You can now slide the cylinder all the way down to meet the cases. Note: Make sure you take any rags out of the cases before reassembling!
    You're now at the point in reassembly where you will install your rebuilt head (details in part 2 of this top end rebuild soon to come) with the proper head gasket, and re-install all the items previously removed. Be sure you are following all proper torque specs specified in your manual.
    Head back for part 2 of the the top end rebuild, where we'll show you some great tips on assembling a four-stroke head with new valves and valve springs, re-installing camshaft(s) and timing chain, and checking and adjusting valve clearance.
     
    Our new ProX piston and freshened up clyinder successfully installed. Note the dot on the piston crown, indicating that is the exhaust side.
    Stay tuned, more rebuild tips to come!
    GasItandCrash
    The pruner and saw are pretty easy to carry.  The lopper is more problematic.  Here is how I carry mine.  So far carrying it here has been a total non-event.  It hasn't  caught on anything or interfered with my riding in any way.
    There are two velcro material loops (https://www.harborfreight.com/3-4-quarter-inch-x-35-ft-roll-hook-and-loop-cable-strap-96215.html)  holding the Lopper.  The one on the riders right is looped through the handguard and is just large enough to slip the blade of the lopper through.  The one on riders left just loops around the metal of the handguard  It is adjusted to that the "top" handle of the lopper will fit in it when the blade is in the other.  The bungee holds the lopper firmly against the headlight. 
     

    To install the lopper I hold the lopper upside down,  I slide the "top" handle through the loop on the riders left.  Then insert the blade in the loop on the riders right.  I then swing the lopper down so that the bottom handle sits on the headlight plastic and connect the bungee.  One hook on the bungee hooks to the handguard metal, then down around the lower headlight mount, up and around the "bottom" lopper handle then around the handguard metal, and back to hook on the "bottom" handle of the lopper.
     

     
    By inserting the blade in upside down and then rotating it down captures the curved portion of the blade and keeps the lopper from moving left to right.
     

     
    You can see that the riders left velcro loop is loose.  That loop is probably unnecessary, but at least it will hold the lopper somewhat in place if the bungee fails.  The lopper might flop around in that case but it won't immediately fall off.
    Yes, carrying it this way has marred the headlight plastic.  I do have a piece of velcro material around the "bottom" handle to minimize the marring after I noticed the damage.  
     

    There is a small space behind the headlight plastic that the pruner fits into nicely without interfering with anything.  I put a rubber band around the clutch tubing and looped it over the pruner handle to keep it from jumping out.
    That's it.  I hope it gives you some ideas on how to carry your tools.
    Good Luck
     
    MotoTribology
    The short answer is no, unless there is a very good reason for it.

    The long answer includes explanations as to why the answer is usually no and can be read below.

    Aftermarket or over-the-counter (OTC) oil additives come in a few general variations:
    Performance Additives Viscosity Modifiers Cleaners Inhibitors Magic & Sci-Fi There can certainly be other types, but a vast majority of OTC additives fall into one of these categories.

    Performance additives generally include anti-wear, extreme pressure, and friction modifying additives. They often have some root in traditional oil formulations; meaning they are commonly used in existing oil formulations and advertised as "performance boosters". For the most part, as OTC additives, they are unpredictable at best, the marketing claims for their performance is rarely supported by any credible evidence, and they usually don't live up to the expectations.

    A big problem is: more rarely equals better for these additives, and simply adding them does not increase the advertised performance reliably. Many of these types of additives experience diminishing returns with regard to performance and their proportion of the lubricant formula. Other groups of them actually experience decreased performance with increased concentrations. So adding them to oils that already have additives providing this performance results in neither additive groups doing the job right.

    Another problem with these additives is their ability to disrupt the surface activity the additives of the original lubricant were designed to do. So by adding one of these chemicals, it is likely to diminish the original performance of the lubricant and substitute it with a potentially less effective replacement.

    There are undoubtedly many anecdotes of these types of additives doing good, but that is more than likely due to either luck or a placebo effect. Every oil formula is different and adding these random amount of random additives is unpredictable at best without knowing the original oil formulation and exactly what you are adding at what quantity. No additive I have ever come across would work in every formula at the exact same concentration.

    Viscosity modifiers are typically either high viscosity oil or a polymeric fluid. They are usually un-additized and therefore dilute the original lubricant's additive concentration. This is bad for similar reasons stated above regarding changing the additive concentrations. By changing the formula concentrations, you may be changing performance aspects that were balanced in the original formula to an unbalanced concentration. These additives can be useful in a few circumstances though. They can be temporary fixes to compression issues and leaks, but even in fixing those problems, you may introduce unintended consequences such as engine efficiency and oil supply through the pump. If it is the only way to get the bike somewhere for maintenance, it might be the best option, but still not good for normal use.
    Polymer fluids in motorcycles add an increased risk. The increase in viscosity is usually very temporary because these polymers are not often shear stable. So once they shear, you have no increase in viscosity and a diluted bulk of oil. So it is a lose-lose in that situation.

    Cleaners come in two main varieties: detergent/dispersant additives and flushing compounds.
    Detergents and dispersants are similar to the performance additives in the sense that they are very surface active and can disrupt the surface active additives of the original oil to its detriment. Detergents, dispersants, anti-wear, and friction modifiers are carefully balanced in oil formulas and increasing the detergent concentration can prevent those other additives from interacting with the metal surfaces where they normally would. Generally speaking, unless you have an engine in absolutely terrible shape, with regard to sludge and carbon deposits, a good oil already has more than enough of these additives in it to do the job.

    Flushing compounds are usually some sort of high solvency fluid meant to dissolve sludge and carbon deposits in dirty engines. These can be useful in very dirty and neglected engines as long as care is taken not to overdo it. If an engine has a high level of sludge and deposits, it is possible to release too much all at once and cause unintended harm by blocking oil flow or forcing that bulk of contaminants into areas it can do harm. So an engine flush can be useful, but care should be taken when doing so.

    Inhibitors usually take the form of antioxidants. These are safer than some other additive types because they aren't generally surface active chemicals. They do still dilute the overall additive concentration somewhat and can possibly throw off the balance of a formula to produce worse overall performance though. There is less risk in using these types, but still, your typical oil should have more than enough antioxidant additives in it to begin with and there is rarely a need for more to be added.
    One final thing I'll cover here is the "magic" and "sci-fi" group of additives. These are the types that usually make some pretty unbelievable claims. They are usually unbelievable for a reason; because they are nonsense. The claims by the "manufacturers" (usually marketers, not chemical manufacturers) are very lofty, always unproven and supported by anecdotes, and typically backed up by lots of buzz words and little substance in any true technical sense.
    Typical claims are:
    large increases in power and efficiency rebuilding of metal surfaces from the inside out fixing leaks with no effect on any other property of the oil "nano" (This prefix above all other things makes me cringe and look closer at marketing claims. Yes I will admit I am prejudiced against "nano" materials in lubricants, but I will also be the first to admit it when I see one that is proven to actually work as advertised.) Typical results are:
    nothing harm benefits claimed with zero evidence lighter wallet and again, nothing For a motorcycle with a wet clutch, one thing to especially look out for with any additives is whether it will affect the clutch. Some additives are right up front with it and say not to use it with a wet clutch, but others are less obvious.
    So in summary, yes there are a few circumstances where benefit can be had from using an OTC additive. In most cases though, there's not much to gain and they either result in a performance decrease or no change at all.
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