Short length of brass tube, a short piece of old broken speedometer inner cable, and a nut from the rejects bin. Welded the nut to the cable inner, and soldered the other end to the fuel screw using the brass tube as a connector. Didn't need or fab up a holder for the end, but could have. Works great, highly recommended mod.
Short length of brass tube, a short piece of old broken speedometer inner cable, and a nut from the rejects bin. Welded the nut to the cable inner, and soldered the other end to the fuel screw using the brass tube as a connector. Didn't need or fab up a holder for the end, but could have. Works great, highly recommended mod.
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!
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.
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.
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?
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.
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.
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.
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.
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.
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.
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
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
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
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
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
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.
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:
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
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.
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.
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.
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.
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!
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.
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.
Putting in the time and money to rebuild your motorcycle engine is both a critical job and a prideful accomplishment. The feeling of an engine failure right after a rebuild is a sinking one, and will most likely stir up a mixture of frustration and disappointment.
We want to help as many people as we can avoid that feeling. So, we've put together a review checklist for your rebuild, followed by a general engine break-in procedure, because your motorcycle should bring joy and fun to your life, not take tufts of hair out of your head.
We'll start with a quick review on the motorcycle top end rebuild. Be sure these critical steps and precautions have been taken. If you find any concerning discrepancies, it's worth it to pull back apart and double check.
Be sure that you have proper piston to cylinder clearance. Recently, a cylinder was bored with requested .0035” clearance. This machine shop has been in the area for over 30 years. When complete, it looked like it was tighter. He slipped the piston through the cylinder a few times and said, "It's okay." He was asked to check again, which he refused, and said that it was correct, and that he was too busy. Back in the Brew Bikes shop, it was double-checked, and clearance was .0015”. Yes, way too tight. Don’t just take someone’s word that clearance is correct, always double check it!
Always double check your piston-to-wall clearance.
Was the honing of the cylinder properly done? Honing is required to be done after boring, and if the cylinder was not bored, it still is needed to deglaze the cylinder for proper ring break-in. Different honing tools are better used for different applications, with common tools being brush hones and flex hones. Safe grits and hone materials depend on the cylinder finish, so check your manual or with the cylinder shop for a recommendation. Be sure that the crosshatch is at 45 degrees. The proper crosshatch will retain the proper amount of lubricating oil while allowing the rings and piston to break-in. Too little of crosshatch or too much will not allow the rings to break-in correctly and never get the proper sealing they were designed for. Read our full guide to cylinder prep.
After proper honing and deglazing, your cylinder wall should have a consistent, 45 degree crosshatch.
If the bike is a 2 stroke don’t forget to chamfer the ports. If it has a bridge in the exhaust port, most pistons require this area to be relieved. READ the piston specs, and if you don’t understand, be sure to reach out to Wiseco for specifications. Read our guide to relieving the exhaust bridge in 2-stroke cylinders.
A critical step in 2-stroke cylinder prep is port edge relief and exhaust bridge relief. This will help ensure smooth piston and ring operation, and combat accelerated ring wear.
Be certain that the ring gap is within specification. Don’t assume it is correct, check it.
Always double check your ring end gap. With your compression ring in the cylinder, measure the end gap with a feeler gauge to ensure it's within the spec included in your piston instructions.
Proper cleaning of the cylinder. Before you start cleaning make sure the gasket areas are clean with no residue of gasket or sealers. First, use a cleaning solvent with a brush and then again with a rag. This is not enough, and you will need to clean with dish soap and water. Using a clean rag you will be amazed on how much grit from the honing is still in the cylinder. Be sure to clean the piston also.
Thoroughly cleaning your cylinder for a rebuild is critical. Be sure all old gasket material is removed, and use a 2-step cleaning process of solvent with a brush and rag, followed by soap and water. When the cylinder is clean and dry, you should be able to wipe the cylinder wall with a clean rag and not see any honing material residue.
Then before assembly, use plenty of assembly lube on the cylinder and the piston. Don’t forget to lube the piston pin and bearing along with the rings.
Assembly lube on the piston, rings, cylinder, pin, and bearing is important for proper break-in.
Many rings have a topside for proper sealing. Double check this and be sure the proper ring is on the proper landing on the piston. Again, read the instructions that came with the piston.
Piston ring markings vary, but the marking should always face up when installed on the piston.
The gaskets and quality play an important part of engine rebuilding. If a gasket is thicker than the original, it could result in a loss of power. Worse yet, a gasket thinner than the original will result in less deck height (piston to head clearance). This reduced clearance may result the piston to come in contact of the head causing permanent damage. After placing the gaskets, be sure while assembling the piston in the cylinder that the ring gaps are in proper placement. Check your engine manual for proper placement of the piston gaps. Then, install the head.
Many motorcycle manufacturers have a desired head nut tightening sequence. Refer to their procedures while doing this. Most companies give the head nut torque rating with the washers, nuts and studs being clean and dry. That means if you use oil or a thread locking compound the studs will be over-stressed due to the over-tightening of the head nuts. Engines have been damaged by this. Now you know, follow what the engine manufacturer recommends!
Regardless of the type of motorcycle engine you're working on, there should be a tightening sequence and torque spec for the head nuts. Pay close attention to the specs in the manual, as these are critical to prevent damage and for proper operation.
Use the proper engine oil and fill to the proper level. The fuel you use should be fresh and of the proper octane. If your engine is a 2 stroke, mix to the proper fuel/oil ratio. For just about any 2-stroke, whether vintage or a newer, a 32:1 fuel/oil mixture is very common, but check your manual for the recommended ratio. Not only is it important for piston lubrication, but also for the crank bearings and seals.
After all this work has been done, and you feel confident with the rebuild, what else can go wrong?
PROPER ENGINE BREAK-IN!
So many mistakes can happen while breaking in the piston and rings, resulting in rings never properly sealing or/and piston galling. Many builders have their own procedures, but most all do heat cycling for breaking in engines.
Before we get into it, please note that this is just one of many methods that work well for engine break-in. Many people have many different effective methods, this is just one example that has worked well for us.
Use this break-in procedure as a guideline for your next fresh top end:
It's important to ask yourself if the rebuilt engine is still using the same carburetor, air cleaner, exhaust system, cam, compression, or if a 2-stroke, the same port work configuration? Any changes can result in air/fuel mixtures to be either too rich or too lean, resulting in engine damage. If your engine is fuel injected and in good working order, the ECU and O2 sensor should keep the air/fuel mixture correct. If you have access to an air/fuel meter, or if a 2-stroke, an EGT (Exhaust Gas Temperature) gauge, check the air/fuel mixture. Even with these tools, spark plug readings are still recommended.
Spark plug readings are a sure-fire way of knowing if your engine is running too lean or too rich. We'll get into more detail in a later article, but generally the plug will look white when it's too lean, and dark brown or black and wet when too rich.
At first start up, keep the engine just above idle and give it a few revs up and down. This power on and power off RPM breaks in the piston and rings evenly on the intake and exhaust sides. If air cooled, once the engine builds up heat where it becomes too hot to touch, shut the engine off. If water-cooled, once the engine coolant starts rising in temperature, shut the engine off. This initial warm up takes just a couple minutes.
Now wait a few minutes until the engine is slightly warm to the touch, repeat #2, letting the engine get slightly hotter. Be sure to keep the engine RPMs above normal idle and keep the RPMs going up and down slowly. Let it cool again till it is slightly warm to the touch.
This time, start and run longer until the engine gets near operating temperature. If air cooled, be sure you have a fan pushing air from the front. You now can rev the RPMs up a little higher, being sure not to hold it at a sustained RPM, but revving it up and down.
Let the engine cool completely. Check all fluid levels to be sure there is no loss of engine lubricant, or, if water-cooled, engine coolant. After engine is cool, do a plug reading to be sure it is not running lean. Because the engine has run a few heat cycles, the gaskets may have compressed. It is VERY IMPORTANT to be sure engine is totally cooled down, and then check the torque of the cylinder head nuts. Most times the cycling head nuts will need some re-tightening. DON’T over-tighten; just tighten to manufacturers’ specification as you did when assembling the engine.
Next, warm up the engine for a couple minutes as you did in the other procedures. Ride the bike, revving the engine up to normal riding RPM. Be sure NOT to keep the RPM too low and don’t lug the engine. These low RPM’s actually puts much more stress on the engine parts. If this is a dirt bike, running on a track is best due to the up and down RPMs the engine will experience. Don’t be afraid to run it normally. If this is a road bike, a curvy road is best due to the RPMs going up and down, this is a must! Don’t lug the engine and don’t go on an open highway that keeps the engine at a sustained RPM. This first initial ride will only be about 5 minutes. Let the engine cool till you can touch the engine.
Follow the same procedure as above, but this time running for 10 minutes.
This will be your last break-in run. Follow the above procedure and run for 15 minutes.
Now is the time to let the engine totally cool down again. Check the fluids as you did before after the engine has completely cooled down, and do another spark plug reading. It is now time to do another check of the cylinder head nuts for proper torque. Sometimes no additional tightening is needed, but don’t be alarmed if you need to, because this is normal
Check all your fluids once more after the engine cools, inclduing coolant and oil level. At this time, the rings and piston should be broken in. Go out and ride it. The first few times, just be sure not to get the engine overheated, but your ride times are not restricted. It never hurts to do another spark plug reading and double-check the head nuts after your first long ride. Enjoy your rides, and be safe!
1. Gearing I Run a 16 tooth front sprocket and a 37 tooth rear. And you can go all the way down to 35 tooth if you wanted to slightly modify the rear hub. I would advise against this. My opinion, a with mildly modified DRZ(exhaust and 3x3 mod) I would not go with taller gearing than 16-39 or 15-37.
2. Rear Tire, You can run up to 160/60 R17, My opinion 150/70 R17 is the best handling.
3. Rewiring Charging cable, by shortening and using a thicker gauge wire that is routed from the battery over to the starter relay and then back into the loom. As well as bringing down the Fuse AMP down to 15amp. 15amp is enough to operate 100 watts of light.
4. 4mm Stroker, Can be installed using the stalk piston and 91 pump gas. 5mm stroker needs to modify the crank case and replace the piston.