Paul Olesen

Experts
  • Content count

    199
  • Joined

  • Last visited

Community Reputation

226 Excellent

1 Follower

About Paul Olesen

  • Rank
    TT Powertrain Expert

Contact Methods

Profile Information

  • Gender
    Male
  • Location
    Wisconsin
  • Interests
    Racing motorcycles, engine design, homebuilt motorcycles, engine building, traveling, flying, backcountry snowmobiling, water sports, downhill mountain biking, reading, and films

Recent Profile Visitors

3,756 profile views
  1. You're welcome, I'm glad you enjoyed the article.
  2. Bell's book is insightful, however, there are many other developers and contributors that should be reviewed as well when discussing modern two-stroke tech. Here are a few: Neels Van Niekerk Frits Overmars Jan Thiel Wayne "Wobbly" Wright
  3. I wrote a book about four stroke engine building titled: The Four Stroke Dirt Bike Engine Building Handbook, which may interest you. If you follow the link you'll you can read more about the book. I appreciate the suggestion and will consider doing a post on the four stroke cylinder head.
    What is it? The Nuetech Tubliss tire system is a dual pressure chamber system that replaces conventional inner tubes and rim locks. Nuetech claims their Tubliss system allows a rider to run lower pressures, improves traction, is lighter than HD tubes, makes pinch flats a thing of the past, protects the rim better, and lasts longer than conventional tubes. First Impressions The front and rear Tubliss tire systems came neatly packaged and ready for installation. Each system included a high pressure bladder, tire liner, integral rim lock, rim plugs, rim tape, installation tool, and instructions - everything necessary for mounting. Overall, the Tubliss system felt and looked like a robust product. The Setup The Nuetech team advised that I would need new tires in order for the Tubliss system to work properly. The reason for this is because conventional rim locks leave indentations in the tire’s bead that make it impossible for the Tubliss system to function correctly. I leveraged the Nuetech team’s experience with their product and put traction’s fate in their hands. I shared with them that hare scramble racing in Southeastern Wisconsin brings a wide variety of terrain including sand, mud, rocks, roots, and occasionally nice tractable dirt. They set me up accordingly with the following tires. Front: Shinko 546 90/100 - 21 Rear: Shinko 505 Cheater 110/100 - 18 I was informed that tire selection is critical for successful implementation of the Tubliss system. When running lower tire pressures the stiffness of the sidewall plays a huge role in how the tire behaves, which makes or breaks the riding experience and, in some cases, the durability of the Tubliss system. Using a tire sealant, such as Slime, is optional but I did opt to do so when I mounted my tires. Installation Installation of the Tubliss system is significantly different than that of a regular tube, rim lock, and tire. Fortunately, a comprehensive set of instructions are supplied which include detailed pictures and references to online videos. The installation process consists of approximately 7 well outlined steps which are not overly difficult to execute. Viewing the online videos was incredibly helpful and made the supplied printed instructions feel more supplemental than essential. A handful of tools/lubricants were required to mount the tires which included: 7/16 drill bit (used to make a hole in the rim for the additional valve stem) Armor-All tire shine Dish soap and/or tire sealant tire irons 120 psi capable air source Overall, I did not find mounting the tires with the Tubliss system installed any more challenging than a conventional setup. In terms of time, I spent a short afternoon removing my old tires, inspecting the condition of my rims, and implementing the Tubliss system. In Action Prior to installing the Tubliss system I had three races under my belt in this year’s hare scramble season which allowed me to have a sort of benchmark using a conventional setup. With the Tubliss system installed I participated in six races and numerous practice sessions, logging a total of over 20 hours with the system installed. Due to Nuetech’s claims about the many advantages of the Tubliss system I wanted to put ample time on the Tubliss system and new tires prior to reporting so that I could feel confident in assessing both performance and durability. Traction and Tire Pressures Soil types and conditions varied throughout the race season. Many of this year’s events were either partly or completely wet and soils ranged from dry sand to muddy clay. One could not ask for a more broad spectrum of conditions to test a new set of tires in. With conventional tubes I normally ran around 10 - 12 psi tire pressure. Right from the start I halved those values and experimented in the 4 - 7 psi range for both the front and rear tires. In general, I felt the tires responded well to reductions in pressure. While traction is difficult to quantify, one of the most memorable parts of the racing season this year were the starts of all the races, and in particular, my first race with the Shinkos and Tubliss system installed. To put things in perspective I’m a mid-pack finishing B-class racer, however, I consistently was in the top five when it came to position after the start of the race. While there are many factors that dictate how good of a start a rider gets, I do believe the Shinkos and having the ability to run them at low pressures had an effect on how well I started. In my first outing with the Tubliss system installed I noted more grip going in and out of corners and had a lot more confidence on the bike than previously with my old setup. On more than one occasion I gained significant ground on other riders while climbing hills and navigating muddy terrain. In general, I felt this combination of tires and pressures responded very well to all the different conditions I encountered. Pinch Flats and Rim Protection I used to suffer pinch flats quite regularly with other setups, however to date, with the Tubliss system I have had no issues. I have run my Tubliss equipped tires into square cornered cement slabs at speed with no ill effects, blasted into logs, and slammed into countless rocks. One of the interesting things that happen when striking a sharp-cornered object with Tubliss equipped tires is that you can literally feel the tire deform and the high pressure bladder absorbing the blow. Maintenance Once installed the only maintenance that Nuetech suggested was to regularly check the tire pressures prior to going out for a ride. I did this religiously but never noted any pressure drops in the high and low pressure chambers. Pros Excellent customer support Significantly improved traction Great pinch flat protection Easy to install Easy to maintain Pressure adjustment down to 0 psi Expensive tires are not necessary Cons Honestly, I've got nothing to complain about. Conclusion I don’t typically rave about products but after my experience with the Tubliss tire system this is one I wholeheartedly endorse. The impact the Tubliss system, equipped with the right set of tires, had on the level of traction I experienced was phenomenal. The fact that the Tubliss system appears impervious to pinch flats is icing on the cake. Adding the Tubliss system is a recommendation I will be making to anyone who will listen and ranks right up there with setting up the bike’s suspension for the rider’s weight, skill level, and discipline. Since the Tubliss system is sensitive to the type of tires used I would highly recommend that anyone considering installing the system do their homework or work with Nuetech on selecting the best tires for their application.
  4. This week I want to talk about two-strokes. To kick off this post I have some awesome news. The Two Stroke Dirt Bike Engine Building Handbook is off to the printers and will be available for pre-sale very soon! Getting the book off the ground has been no cake walk. It's been two years coming and we are so thankful our riders and fans have been patient with us! At the end of this post I'll give you instructions on how you can stay updated on the launch. With that said, let's get started. Today's post aims to provide an overview of the important aspects of the two-stroke cylinder and answers a couple commonly asked questions relating to cylinder modifications. The ports found within a two-stroke cylinder in combination with the exhaust system have the greatest influence on power, torque, and the RPM at which maximum power is created out of the various engine subsystems found within a two-stroke engine. Typically when a new engine is designed the port characteristics are one of the first parameters to optimize. With this being the case they are also one of the first things anyone planning on altering an existing engine should consider improving or tailoring to their specific application. A two-stroke cylinder consists of exhaust, transfer, and occasionally inlet ports (true inlet ports are only found on piston or rotary valve controlled engines). The port heights, widths, areas, directions they flow, and relationships to one another all have a significant influence on how the engine will behave. The cutaway of the cylinder shown details the port arrangement and common nomenclature. The inlet port/passage delivers air into the engine’s crankcase, most commonly through a reed valve, on a dirt bike engine. On older engines, a rotary valve or the piston may also be used to control the opening and closing of the inlet port. On modern machinery, the inlet simply connects the reed valve to the cylinder or crankcase. In this case, the primary restriction in the inlet port is the reed valve and as such the valve’s geometry and flow capabilities often dictate the inlet port's performance. The transfer ports are responsible for moving fresh air and fuel up from the crankcase into the cylinder. This occurs as the piston travels downward after the cylinder has fired. Once the piston uncovers the tops of the transfer ports the blowdown phase is complete, at which point much of the exhaust gas has been expelled from the cylinder. As the transfer ports begin to open, the exhaust pipe sucks fresh mixture up through the transfer ports into the cylinder. To a lesser extent, the downward motion of the piston also aids in creating a pressure differential between the crankcase and cylinder. The shapes and flow capabilities of the transfer ports play a big part in how effectively the cylinder can be scavenged of exhaust gases and filled with fresh air and fuel. The transfer ports also help cool the piston. The exhaust ports dictate how much and how well exhaust gases depart the cylinder. Similar to the transfer ports, the duct shape, angle, length and volume have a large influence on how well gases can flow through the port. Typically, dirt bike engines commonly feature bridge port or triple port designs. General insights into a cylinder’s performance can be made by characterizing attributes such as the timing of the exhaust and transfer ports, the port widths, and the directional flow angles, but a deeper analysis is required to truly optimize a cylinder. Today, tuners and designers rely on computer software which computes a port’s specific time area (STA). As defined in the EngMod 2T software suite, “STA provides an indication of the effective port window area that has to be open for a certain length of time to allow enough gas to flow through the port to achieve the target power at the target RPM for the given engine capacity”. STA values are used to quantify the exhaust, transfer, and inlet port geometry as well as the blowdown phase of the two-stroke cycle. The blowdown phase occurs between exhaust port opening and transfer port opening and is one of the most important parameters in predicting engine performance. By manipulating STA values and subsequently the height, shape, and size of the exhaust, transfer, and intake ports, an engine’s power characteristics can drastically be altered. Port modifications can be made which allow more air to move through the cylinder, ultimately increasing the power of the engine. Conversely, ports can be filled or welded and reshaped which tame the engine and provide less peak power but a broader spread of power. Simple modifications to the ports can also be carried out which improves the air or exhaust gas flow through the port yielding better cylinder scavenging. Can I modify my own cylinders? Unless you have a deep passion for two-stroke tuning, are willing to spend money on software and porting equipment, and are comfortable throwing away botched cylinders, I would recommend having a reputable professional carry out any desired port modifications. Experienced tuners have developed a number of porting combinations that will work well for various makes/models and riding applications which will take the guesswork out of the situation and provide you with a good performing cylinder. Who should consider two-stroke porting modifications? For the sake of simplicity, I will lump porting modifications into two categories: major and minor. Major port modifications would include tasks such as significantly changing the port timings (by either removing or adding material), altering the shapes of the ports, or changing the directions the ports flow. Anyone drastically altering their engine, such as turning an MX engine into a road racing engine, should consider major porting modifications. Other examples of applications that may require or benefit from major port modifications include drag racing, hare scrambles, ice racing, or desert racing. Minor port modifications would include basic tasks such as removing casting flash, slightly altering the ports to achieve the stock port timing, and correcting areas that result in minor flow deficiencies. Just about everyone could benefit from these types of corrective actions; however, if the engine is already performing or producing adequate power, they often aren't considered. I hope you enjoyed this writeup on key features affecting the performance of two-stroke cylinders. To stay officially updated on The Two Stroke Dirt Bike Engine Building Handbook we created an email sign up for our readers. Click this link to see the new cover, the Table of Contents, and some sneak peek pages right from the book. Thanks for reading and have a great rest of your week! -Paul
    What is it? The Technology Elevated SmartCarb is a carburetor capable of self-compensating for changes in ambient air density. Put another way, the carburetor automatically alters the mixture when there are changes in temperature and altitude. This functionality eliminates the need to continuously adjust jetting throughout the riding season or when riding at locations with varying elevation. Technology Elevated also boasts that the carburetor improves fuel atomization which leads to increased power, better fuel economy, and reduced emissions. First Impressions The SmartCarb arrived in an elegantly constructed box which ensured it would not get banged around in transit. The SmartCarb itself consisted of cast and billet machined components and came with everything required for installation. Also included was a nice instruction booklet with nearly 60 pages of installation and tuning detail, an extra float bowl gasket, and Technology Elevated stickers. Lastly, on the back of the instruction booklet, all the factory settings were recorded so the customer can revert back to the baseline settings at any time. Applications Anyone with a two or four-stroke carbureted engine could have a reason for considering the Smartcarb. The carburetor could be especially useful for riders who routinely transition through varying elevations or ride in places with large temperature swings since the carburetor automatically adjusts for changes in ambient air density. The Setup I installed the 38mm SmartCarb on the bike I race hare scrambles with, which is a 2007 Yamaha YZ250. The engine is equipped with an FMF Fatty pipe, Rekluse clutch, and weighted flywheel. Apart from these items the engine is stock. The engine was recently rebuilt this past winter and at the time of installation it had 14 hours on it. Installation Installation was easy and the necessary instructions were clearly outlined in the instruction booklet. Anyone capable of performing basic maintenance on their vehicle will be able to tackle this project. During the installation process there were no noteworthy issues or challenges and in total, installation took around an hour. Initial Tuning The design of the SmartCarb and provided installation booklet attempt to make tuning the carburetor as easy as possible. The SmartCarb is designed so that the user only has to tune the idle and low speed fuel/air mixture. The rest of the tuning parameters are set up at the factory and are tailored to the user’s specific make and model of engine. Two easily adjustable features on the SmartCarb can be utilized to make alterations. The idle set screw is used to raise or lower the slide and allows more or less airflow through the carburetor. The clicker adjuster raises or lowers the fuel metering rod which increases or decreases the amount of fuel that flows into the venturi. The idle set screw is simply turned clockwise or counterclockwise to make adjustments. In order to adjust the fuel metering rod with the clicker adjuster, the engine must be off and the throttle must be held wide open. The clicker adjuster can then be depressed and turned until it engages with the metering rod, at which point, the metering rod height can be raised or lowered depending on the direction the clicker is turned. The tuning instructions and recommendations presented in the instruction booklet are thorough, detailed, and laid out in a way that makes them easy to follow. For the sake of the review, I attempted to set aside my personal tuning experience and perform the process as a relative newbie, relying primarily on the provided instructions to make tuning decisions. I spent an afternoon carefully studying the tuning instructions and test riding the bike before I was satisfied with the state of tune of my Yamaha. While my overall impression of the tuning instructions is favorable, I did feel in some instances the instructions were too literal. Once I got the low-speed mixture dialed in the engine ran excellent. Power delivery was smooth, the engine sounded good, and there were no signs of rich or lean conditions anywhere throughout the throttle range. After accumulating enough runtime to feel comfortable that a spark plug reading would result in an accurate assessment I pulled the plug and took a look.The spark plug confirmed what my senses and past experiences have told me was a properly jetted two-stroke engine. In Action I have spent around 15 hours of riding and racing my bike with the SmartCarb installed. Initially, I set the carburetor up on an 80°F day and have ridden in temperatures as high as 93°F and as low as 45°F. I participated in five races, each of which had different types of soil conditions, which subsequently loaded the engine differently. Most notably, in the last two races I participated in, the courses were littered with deep sand which caused the engine to run hotter than normal. After my first tuning session I anticipated some adjustment may be necessary once I really put the bike through its paces. The first race was a good test for it and led me to make further clicker and idle adjustments. I found that when tuning it is very important to tune in race like conditions and keep the engine up at operating temperature. The biggest challenge I faced with the SmartCarb was maintaining a consistent idle. This may sound alarming, however, there is a caveat to this. The Rekluse clutch I have installed puts more load on the engine and has an impact on how the engine runs at idle and low speed. I have been working with Corey Dyess, the founder of Technology Elevated, throughout this review to work through this tuning anomaly. Taking his advice I have been able to significantly improve the situation by making small changes to the SmartCarb settings and am now operating in a much better place. We believe we may be able to improve the tune further by installing a fuel metering rod with a different profile, however, at the time of writing, this change has not been implemented. Throughout the race season, apart from the noted idle issue, performance has been spot on. The engine has run great and I never experienced any abnormal mixture conditions. Due to the heavy load deep sand puts on engines I did have to slightly richen my mixture in the last race of the season to compensate, which wasn’t necessarily unexpected. All-in-all I was extremely pleased with the low/mid/top end performance of this carburetor and loved having near perfect jetting in all atmospheric conditions. Pros Excellent state of tune through RPM range Compensates for changes in ambient air density Clicker adjuster makes it easy to qualify how much adjustment is occurring Factory settings are recorded on the back of the instruction booklet Customer support is great Can be tuned with no tools Can be tuned in place on the bike even with an oversized fuel tank installed Minimal adjustments required after installation Cons Tuning instructions cannot be taken too literally Conclusion The Technology Elevated SmartCarb is a good option for anyone looking for a carburetor that auto compensates for changing ambient air density. While I was unable to work all the small tuning details out pertaining to my specific setup prior to concluding this review I am still impressed by the SmartCarb. The fact that jets no longer need to be swapped out whenever conditions change and that the carburetor is extremely easy to adjust is great. Factory support is excellent, Corey is very knowledgeable about his carburetor, and he is willing to help optimize specific engine setups. I am a fan of this carburetor and believe that it could be beneficial to a lot of riders, assuming they are willing to take the time to dial it in.
  5. 2 reviews

    The SmartCarb is the culmination of more than 45 years of development of the single-circuit, flat-slide carburetor by renowned carburetor expert and inventor William H. Edmonston. Its pedigree comes from the long line of Edmonston-designed carburetors, including the Lake Injector, Pos-a-Fuel, Ei Blue Magnum, Quicksilver, and Lectron. The SmartCarb combines the best features from earlier flat-slide, variable-venturi carburetor designs and incorporates design features developed by Technology Elevated, making it a real world solution to satisfying emissions regulations and OEM performance requirements in small engine applications worldwide. Technology Elevated is currently focused on the off-road 2-stroke and 4-stroke powersports market, offering 25, 28, 36, 38, and 40mm SmartCarb sizes. Application driven development is underway, most recently involving testing for integration in UAVs, mini-motocross bikes, alcohol junior dragsters, micro-sprint carts, snowmobiles, paragliders, and outboard marine engines. The SmartCarb has proven itself to be viable in leisure and competitive applications and is capable of competing directly with electronic fuel injection for both passing emissions regulations and meeting performance requirements.
  6. Today I want to share some pointers on preparing new or re-plated cylinders that will help ensure your engines run stronger and last longer. Plus, I've got an update on the two-stroke book I've been working on that I'd like to share. Let's get started! A Universal Concern First, both new and re-plated cylinders must be cleaned prior to assembling. Normally the cylinders will arrive looking clean, but looks can be deceiving. I have no doubt that the factories and re-plating services clean the cylinders as part of their processes, but I highly recommend cleaning the bores a final time prior to use. Shown below is a new Yamaha cylinder that I extracted quite a bit of honing grit out of. If left in place, the honing grit will ensure that the piston rings will wear out faster than they need to, so be sure to take the time to properly clean new cylinders prior to assembly. What’s the best way to clean the cylinder bore? Start by using warm soapy water and a brush to clean the cylinder. Take your time and be thorough. After the majority of the honing grit has been removed switch to automatic transmission fluid and a lint free rag for one final cleaning. As a test to check cleanliness, rub a cotton swab against the cylinder bore. If the swab picks up any debris and changes color, your cleaning duties are not over. The swab should be able to be rubbed against the bore and remain perfectly clean. Two-Stroke Port Dressing For two-stroke owners, the second item I want to bring to your attention is port dressing. Port dressing is a term used to describe the process of deburring/breaking the edge at the intersection of the cylinder plating and the ports in the cylinder. During the plating process, plating usually builds up excessively at the edge of the port and must be removed after honing. Proper removal is critical to ensure acceptable piston ring life. Manufacturers and plating services will break the edge in different ways and to different magnitudes, which ends up being a whole other topic. The important thing is to ensure that any new or re-plated cylinder you use shows visible signs that the port edges have been dressed. A dressed port edge will be easy to spot because it will feature a different surface finish than the cross-hatch created from honing. This is easily visible in the image shown above. Many port dressing operations are done manually so some irregularity in the geometry will usually be present. If there is no visible edge break on the port edges, I would be highly suspicious and contact the service that plated the cylinder or sold the cylinder and confirm with them if a step was missed. Typically a chamfer or radius in the .020 - .040” (0.5 - 1mm) range is used. Two-Stroke Power Valves Lastly, it is possible that some of the power valve components, such as blades or drums, will not fit correctly on cylinders that have been replated. This is because the plating can occasionally build up in the slots or bores where the power valve parts reside. Prior to final assembly, be sure to check the function of the power valve blade and/or drums to ensure they move freely in their respective locations within the cylinder. If plating has built up in a power valve slot or bore, it will need to be carefully removed. To do this, appropriately sized burs for die grinders or Dremel tools can be used. If one is not careful, irreversible damage to the slot or bore can result. When performing this work proceed cautiously or leave it to a seasoned professional. Burs for the job can be difficult to track down in stores, but are readily available online from places like McMaster-Carr. When purchasing burs, be sure to pick up a few variants, such as rounded and square edged, designed for removing hard materials. The Two-Stroke Book From February to March we photographed the entire book. From April onward we have been formatting and proofreading. Needless to say, we are in the final stretch! If you want to stay updated on the moment the Two-Stroke Dirt Bike Engine Building Handbook is ready for pre-order, sign up at the link below. We can't wait to get this book out the door and into your garage. Sign Up for Updates on the Two-Stroke Book Thanks for reading and have a great rest of your week! -Paul
  7. I have a 1995 kx250 with a shot jug. I have a nice fresh ported and polished jug off a 2000 kx250. Will the 2000 jug work with the 95 motor? Thanks in advance.

  8. Today I'm going to cover how to check and set cam timing, which is something you can do if you have adjustable cam gears in your engine. This is a procedure often performed by race engine builders to ensure the valvetrain performs just as they intend, and ultimately so that they extract the desired performance out of the engine. Adjustable cam gears typically aren't a stock option but are abundantly available in the aftermarket. The following text is exerted from my book, The Four Stroke Dirt Bike Engine Building Handbook, so if you find this info valuable please take a look at the entire book. Degreeing the camshafts is the process of checking, and if necessary altering, the cam timing so that the timing is set perfectly to specified timing values. On stock and performance engines, cam timing can be off slightly due to manufacturing variations in parts such as the camshafts, cam gears, cam chain, cylinder, cylinder head, crankshaft, crankcase, and gaskets. With so many parts having an influence on cam timing, it is necessary to adjust and correct the timing so it coincides precisely with the desired timing values. The biggest factor determining how the camshafts must be timed is whether the cam lobes are symmetrical or asymmetrical. Camshaft lobes that are symmetrical have opening and closing ramps that share the same profile. Asymmetrical cam lobes have opening and closing ramps with different profiles. Symmetric and asymmetric camshafts are timed differently. First we will focus on the timing of symmetrical camshafts. Symmetric camshafts are timed most accurately by determining the position of the camshaft’s lobe center in relation to crankshaft position. A camshaft’s lobe center is where peak lift occurs, which is the most important timing event of the camshaft. Since the tip of the camshaft is rounded, it would be difficult to determine the lobe center by taking a direct measurement of peak valve lift. The opening and closing points of the camshaft are also of little use because the cam opens and closes gradually. This makes it difficult to determine the precise position in which the camshaft opens or closes the valves. The lobe center position is a calculated value based on the position of the camshaft at two specific points of valve lift, typically with valve clearances set to zero. Normally the position of the camshaft is recorded at 0.050” (1.27mm) of lift as the valve opens and 0.050” (1.27mm) of lift when the valve closes. By recording the position of the camshaft at a specific valve lifts, the cam lobe is on a predictable portion of the opening and closing ramps. The center of the cam lobe is exactly in the middle of these two measurements. To calculate the lobe center of a symmetrical cam lobe you will need to do the following: 1. Add the measured opening and closing timings together 2. Add 180 degrees to the sum 3. Divide the answer by 2 4. Subtract the smaller value of the two opening and closing numbers from the answer to reach the lobe center value. Once the actual lobe center value has been determined on the engine, it can be compared to the specified lobe center timing presented by the manufacturer, aftermarket cam supplier, or the engine tuner. If the measured lobe center position coincides with the targeted position, all the work is done. If not, the cam gear will need to be adjusted so the timing is corrected. If you are checking the timing on stock cams and lobe center information isn't presented, you will need to determine the lobe centers the manufacturer recommends. To do this, the opening and closing timing information supplied in the service manual can be used. Aftermarket camshafts should come with a timing card full of useful information to set the cams correctly if they are adjustable, otherwise the lobe centerline can be calculated if the opening and closing timings are known. If you don’t like math, there are plenty of lobe center calculators available on the internet you can use. For the Kawasaki KX250F engine with the stock camshafts, the timing information is as follows: Intake Opens 40° BTDC (Before Top Dead Center) Intake Closes 72° ATDC (After Top Dead Center) Intake Lobe Center = ((40 + 72 + 180) ÷ 2) - 40 = 106° My calculated lobe center timing is 106°. When I check the cam timing, this will be the value the real engine hopefully yields. The lobe center for the exhaust cam can be found the same way. For the KX250F exhaust cam: Exhaust Opens 69° BBDC (Before Bottom Dead Center) Exhaust Closes 49° ATDC (After Top Dead Center) Exhaust Lobe Center = ((69 + 49 + 180) ÷ 2) - 49 = 100° Something not obvious I want to touch on is that if the intake opens after top dead center, a negative value for the opening should be used. If the exhaust closes before top dead center, a negative value should be used here as well. To start the process of checking the timing the valve clearances should be set to zero. Thicker shims can be used and zero clearance can be confirmed with a lash gauge. A degree wheel and pointer will need to be installed on the engine. There are many ways of attaching these items and each engine will provide its own challenges. Here I’ve left the flywheel on and installed a couple washers behind the degree wheel to space the degree wheel from the flywheel. Then the flywheel nut is used to secure the degree wheel. The pointer can be made from welding rod, a coat hanger, or anything else you can find. I’ll be finding TDC with the cylinder head installed, so I used one of the exterior head bolts to secure the pointer. If you will be finding TDC with the head off, choose another location. Before the cams can be timed, TDC must be found. This can be done with the cylinder head on or off depending on the process you use. The piston dwells a few degrees at TDC so more accuracy than zeroing the degree wheel to the piston’s highest position is necessary. Similar to finding the cam lobe center, TDC can be found by measuring equal distances on the piston’s up and down stroke and then confirming that the degree wheel timing is equal on both sides at the measured distances. Dial indicators or piston stoppers are commonly used to do this. HOT TIP: Piston stoppers can easily be made by removing the center section of a spark plug and then tapping a suitably sized threaded hole in the remaining part of the plug so a bolt and lock nut can be installed. The stopper can then be easily threaded into the spark plug hole. Whichever method of finding TDC you decide to use, start by moving the crankshaft to the approximate TDC position. Then without rotating the crankshaft move the degree wheel so that TDC on the wheel coincides with the pointer. Next, set up your piston stops or measure piston travel on both sides of TDC. In this example I’m using a dial indicator which extends through the spark plug hole down into the cylinder. I’ve decided to take measurements at 0.050” (1.27mm) of piston travel before and after TDC. At each measurement point the number of degrees indicated on the degree wheel before and after TDC should be the same if I have found true TDC. If the degree wheel values don’t read the same before and after TDC determine which way the wheel must be rotated so that the values become equal. Then carefully rotate the degree wheel without rotating the crankshaft to alter the degree wheel’s position. Once altered, recheck and confirm that true TDC has been found. This can be a tedious process but is extremely important for checking cam timing accurately. Repeat the procedure for checking TDC 3 - 5 times to ensure repeatability and accuracy. After true TDC has been found, be extremely careful not to inadvertently move the degree wheel or pointer. Do not rotate the crankshaft using the nut securing the degree wheel to the crankshaft. Instead, use the primary drive gear nut or bolt to rotate the engine over. Next, set up a dial indicator on the intake or exhaust lifter bucket, depending on which camshaft you are checking. You’ll have to use some ingenuity here in determining the best way to secure the dial indicator to the engine. I’ve used a flat piece of steel and secured it to the cam cap using the cylinder head cover holes. Make sure the indicator travels as parallel to the path of valve travel as possible for accurate readings. Also makes sure at least 0.060” (1.52mm) of travel from the indicator’s resting position is possible so adequate valve lift can be measured. Once the indicator has been set up, the cam timing can be checked. Whenever checking timing only rotate the engine over in the direction of engine rotation. Reversing engine rotation will result in inaccurate measurements due to the reversal of gear meshes and chain slack. If you miss a measurement point, rotate the engine over until you get back to the previous position. Slowly rotate the engine over until 0.050” (1.27mm) of valve lift has occurred. Then record the position of the degree wheel. Next, rotate the engine until the cam begins to close the valve. Once only 0.050” of indicated valve lift remains record the position of the degree wheel. Repeat this process of checking opening and closing positions 3 - 5 times to check for repeatability before calculating the cam lobe center. Once you are confident in your measurements proceed to calculate the cam lobe center. On the KX250F engine my intake lobe center is as follows: Measured Intake Open (0.050” Lift) 39 ° BTDC Measured Intake Closure (0.050” Lift) 74 ° ABDC Intake Lobe Center = (( 39 + 74 + 180 ) ÷ 2 ) - 39 = 107.5° On my stock KX250F engine the actual lobe center is 107.5°. At this point if I had adjustable cam gears, I could rotate the gear slightly so that the lobe center corresponded to the specified lobe center value. The same procedure is followed for checking and adjusting the exhaust cam timing. Remember if mistakes are made when setting cam timing big problems can result, so it is best to be very patient and focused when performing this task. Always check your work 3 - 5 times to make sure the timing is repeatable and making sense. When tightening adjustable cam sprockets, use a locking agent and be sure to torque the bolts to their specified values. When working with single camshafts that have both the intake and exhaust lobes ground on them, focus your efforts on achieving correct intake timing. Correctly setting intake timing is more important since it has a larger effect on power. The intake valves also have higher lift than the exhaust valves, potentially creating clearance troubles between the piston and valve if the intake valves are mistimed. With your new fangled ability to adjust cam timing, you may be wondering what happens if you advance or retard the intake and exhaust cams from their standard positions? The lobe separation angle refers to the number of degrees which separate the lobe center of the intake lobe from the lobe center of the exhaust camshaft. The lobe separation angle can be calculated using the following formula: LSA = (Intake Centerline + Exhaust Centerline) ÷ 2 As a rule of thumb, reducing the lobe separation angle by advancing the intake and retarding the exhaust camshaft will increase valve overlap, move power further up the power curve, increase cylinder pressure, increase the chance of detonation, and reduce the piston to valve clearances. On the contrary, increasing the lobe separation angle by retarding the intake cam and advancing the exhaust cam will have somewhat of the opposite effect. There will be less valve overlap, power will move to a lower RPM, chances of detonation will be reduced, and the valve to piston clearances will increase. The likelihood of finding more or better power by advancing or retarding the camshafts is not all that likely because manufacturers, tuners, and aftermarket companies already test specific combinations of cam timings to death. In addition, if the lobe separation angle is reduced, the piston to valve clearances should be checked to ensure they are adequate. My advice is to run the prescribed cam timings to reduce the chance of problems occurring. Asymmetric camshaft timing can be set in a similar fashion to symmetric camshafts, however instead of focusing on the lobe center position, the specific opening and closing points will need to be measured. Timing cards supplied with asymmetric cams should have specific instructions for setting timing, but normally valve clearance is set to zero and cam positions are recorded at specific lift heights. Based on the measured opening and closing positions, adjustments are made to the timing until the timing matches the specified values. I hope you enjoyed this exert on checking and adjusting cam timing. As always feedback is appreciated so please leave comments below. If you're interested in more engine building info check out my book The Four Stroke Dirt Bike Engine Building Handbook. Right now we are having a 4th of July Sale where everything on our site is 20% off with the discount code fourthofjuly2017. Just be sure to enter the code upon checkout so you receive your 20% off! So if you've had your eye on our Four Stroke Dirt Bike Engine Building Handbook or even our Value Pack, but haven't pulled the trigger yet - go for it! Availabe at: DIYMotoFix.com - Paul
  9. It's time to open up a can of worms and talk about a hotly debated topic in the powersport community - four stroke cylinder head reconditioning best practices. I've perused the forums and had discussions with people about reconditioning four stroke cylinder heads and there appears to be a lot of mixed opinion and beliefs on what is right or wrong. I'm certainly not going to say my take on the subject is the only way, but I do want to share my opinion, explain the technical details, as well as touch on the machining process. The text below is out of my book, The Four Stroke Dirt Bike Engine Building Handbook, and details why cylinder heads should be reconditioned a certain way. Whenever new valves are installed in a cylinder head, it is best practice to recut the valve seats since the valves and seats are mated parts, otherwise the new valves are very susceptible to premature wear when run in the old seats. If a major overhaul is being performed, there is a good chance that enough seat wear will have occurred during the engine’s life that the valve seats will need to be recut before new valves are installed. This may be news to you, so I want to provide an explanation of why this is necessary. The term concentricity is used to describe the relationship between the axis of two circular objects. When two objects are perfectly concentric, their axis match up precisely with one another. In the case of the cylinder head, the valve guide axis and the valve seat axis must be as close to perfectly concentric as possible and parallel to one another. Usually, guide to seat concentricity is kept around 0.001” (0.025mm) or even less for racing applications. This is achieved by the factory by using a manufacturing process where the valve guides are reamed first. Then the freshly reamed valve guide bore is used to center the valve seat cutter. Once centered, the valve seat is cut. This process is then repeated for all the valves and results in very good concentricity between the valve guides and valve seats. As the engine is run, the valve guides, valve seats, and valve faces will wear. The valve guides will wear from front to back in an oval shape at the top and bottom of the guides. In a cross sectioned view the valve guide will take on an hourglass shape. The guide will become oval as a result of thrust forces stemming from the way the camshaft contacts the lifter bucket or rocker arm. These forces are transmitted to the valves and cause the valves to thrust against the sides of the guides, eventually causing the guides to become oval shaped. Once the guides start to become oval shaped, the valve faces will no longer be as concentric to the valve seats as they originally were. When this happens the valves will start to slide against the seats, causing the seats and valve faces to wear. The valve seats will eventually become out of round and the sealing between the valve face and seat will suffer. Installing new valves into oval shaped guides and out of round seats will ensure that the new valves wear out very quickly! To ensure the new valves being installed last as long as possible, the cylinder head’s seats and guides must be reconditioned once they are worn out. Complete cylinder head replacement is always an option, but I want to focus on freshening up the original head which is usually a more economical option, but comes with many more variables surrounding the quality of the job. There are numerous services offered in the marketplace for valve seat cutting, however, not all valve seat cutting methods are equal in terms of quality. There are hand operated seat cutters, dedicated seat cutting machines, and a few other options to choose from. Selecting the correct seat cutting process and entrusting the work to a competent engine builder is very important. The valve seat cutting process should mimic the OEM process as closely as possible. A concentric valve seat will never be able to be cut without first servicing the valve guides. If the valve guides are out of round then they will either be reamed to a slightly larger size if they are not too oval in shape or they will be replaced. Once any issues with the valve guides are addressed and they are perfectly round from top to bottom, it will be possible to cut the valve seat. Ensuring the valve guide is perfectly round is extremely important since the valve seat cutter is centered off of the valve guide bore. Cutting the valve seat concentrically to the guide requires a combination of skill and using modern machinery. The best valve seat cutting equipment in the world is worthless without a good experienced operator running it. There are two main factors which make cutting a seat concentric to the valve guide difficult. To start with, the valve seat cutter uses a pilot which locates in the valve guide. Since the valve stems are very small in diameter the pilots used to guide the seat cutters are also very small in diameter. A small diameter pilot shaft that centers the cutting tool can flex easily, which presents a real problem when cutting the seats. The next issue that arises when reconditioning seats is that often times the cutting tool will try to follow the path of the old valve seat which can make it hard to cut a concentric seat. Couple these factors together with slop within the machine, setup error, and operator error and you can see how quickly things can come out of alignment and you can end up with a poorly cut seat. In addition to seat concentricity, the depth the seat is cut to will influence valve spring pressure, shim sizes, and the compression ratio of the engine. All three of these variables will be reduced the deeper the seat is cut, which is not a good thing. The surface finish of the seat itself will influence how well the valve seals. A seat with chatter marks or other machining blemishes will not seal as effectively as a smooth seat. The valve seat width and the contact point between the seat and the valve face are also very important. Due to the complexities involved with cutting valve seats on modern four-stroke dirt bike engines, the job should not be left up to just anybody. There are numerous businesses which specialize in valve seat cutting which have both the right equipment and expertise to do the job correctly. I highly recommend spending some time researching and finding a reputable cylinder head machining company when it comes time to recondition your head. If the cylinder head must be shipped off in order to do business with a reputable company, the additional wait will be worthwhile. If you found this information helpful and would like more technical info on maintaining your four stroke engine, check out my book, The Four Stroke Dirt Bike Engine Building Handbook. Thanks for reading and happy wrenching! As always if you have comments or want to share your thoughts please leave a note below. -Paul Available at: - Amazon - Moto Fix Website
  10. I hope you all have been out riding and enjoying spring. I got back into the hare scramble racing scene over the weekend after a three year hiatus and had a blast. Today, I just want to share a quick tip and start a discussion on preparatory things that help shorten the time it takes to do complex maintenance tasks, such as rebuilding an engine. Quick Tip Prior to turning a wrench carefully look over the service manual scanning through all the applicable procedures and subsystems. If I’m working on an unfamiliar model, I find it is helpful to jot down a rough outline of the disassembly sequence. This saves me time in the long run as I don’t have to rely as heavily on the service manual or continually flip through various sections. Another option is to use post-it notes to bookmark each relevant section in the manual. Mark the post-it notes with numbers or headings so you know where to turn to next. Earmarking or bookmarking the torque tables is also a huge time saver no matter the task. Be sure to scan through the manual as well to identify any specialty tools that are required that you may not have. Discussion Points What other preparatory things can be done to help speed up the major maintenance process? Is there a method to your madness or do you dive right in? Thanks for reading! Paul https://www.diymotofix.com/
  11. I completely agree with the commentary on prepping the bike before the event. There is no substitute for making sure it is ready to go. Are there things on my list that are overkill, probably, but on the flip side most items don't consume much space so I don't see much down side to squirreling them away in my tote even if the likelihood of using them is minimal. The stuff in the tote stays the same whether going to a one day event or off to a week long destination ride. What's in the tote ultimately can be the difference between just having a bad outing on the bike, to a completely ruined weekend of riding if the right bits aren't available to make a quick repair. Everyone's situation is different so tailoring my suggestions to individual risk tolerance and application is essential. Keep the suggestions and feedback coming!
  12. This month I want to discuss three easy ways to improve engine cooling for your dirt bike or ATV and explain why they are effective. As improvements are made to an engine that increase its power, the amount of heat the engine will create will also increase. Effectively removing heat from the engine and cooling it is very important as the power output of the engine goes up. The cooler an engine runs, the more power it can produce. There are three ways that the aftermarket attempts to improve the cooling system of a particular engine. 1. Increase flow through the cooling system. 2. Increase the cooling capacity of the radiators. 3. Increase the pressure of the cooling system. Let's dive in. 1. Increase flow through the cooling system The flow through the cooling system can be increased by installing a water pump impeller designed to increase the flow rate of the coolant. The reason increasing the flow rate of coolant works is because the rate of heat transfer from the engine to the cooling system is directly proportional to the mass flow rate of coolant. This is thermodynamics jargon, but there are two key parts to consider. First, how much coolant is flowing, and second, at what speed the coolant is flowing. The more coolant that flows and the faster it flows will reduce the temperature difference between the point where the coolant enters into the engine and where it exits. This next part is not quite as intuitive. When the temperature difference between the inlet and outlet is reduced, the average coolant temperature is lowered. When the average coolant temperature is lowered the engine will run cooler. This is why fitting a water pump, which increases the flow of coolant through the engine, improves cooling. 2. Increase the cooling capacity of the radiators Radiators consist of a series of tubes and fins which run from the top to the bottom of the radiator. These are often referred to as the radiator’s cores. As coolant enters the radiator it moves through the series of tubes and heat is transferred from the coolant to the fins. Air passes over the fins and heat is transferred from the fins to the air. This transfer of heat from coolant to air is how radiators reduce the temperature of the coolant. Coolant temperatures can be reduced by upgrading radiators in three ways, by increasing the frontal area of the radiators, by making the radiators thicker, or by using materials with better heat transfer properties for the cores. For all practical purposes, increasing the radiators’ frontal area and improving the core materials is rarely a viable option for dirt bike applications. This is because there is little room for the radiators to begin with and they are susceptible to damage, making the use of expensive core materials a risky affair. Unfortunately, both of these options are better improvements to make before resorting to increasing the thickness of the radiators. Increasing the thickness of a radiator is not as efficient of an improvement as increasing the frontal area of the radiator. In order for thicker radiators to cool more effectively than their stock counterparts, airflow past the radiators is key. When the thickness of a radiator is increased, air must travel a greater distance through the radiator before exiting. The speed the air is traveling plays a big role in determining how quickly the air heats up as it moves through the radiator. If the air is not traveling fast enough through the radiator, the air temperature will rise and equal the coolant temperature before reaching the end of the radiator. Once this happens, heat transfer stops and whatever portion of the radiator remains will not help with cooling. In order for a thicker radiator to be effective, air must flow quickly enough through it so that the exiting air temperature is at, or better yet, below the coolant temperature. In conclusion, benefits from adding thicker radiators will be more prominent in applications where speeds are relatively high. Whereas in applications where the bike is hardly moving, improved cooling may not be noticeable. 3. Increase the pressure of the cooling system The last alteration to the cooling system that can be made is to install a high pressure radiator cap. As coolant temperature increases, pressure increases inside the cooling system. The radiator cap is designed to be the pressure release point in the cooling system in the event that too much pressure builds up. This can occur as a result of overheating or a blown head gasket for example. By designing the radiator cap to be the weak link in the system, other parts of the system, such as seals, don’t end up getting damaged from being over pressurized. The radiator cap features a plug and spring on its underside. The spring is designed to compress once a certain pressure is reached, at which point the plug will move upwards and uncover a pressure release hole where excess pressure will be vented. The coolant’s boiling point and ability to conduct heat are necessary factors in understanding why a high pressure radiator cap can help improve engine cooling. Water alone boils at 212°F (100°C) while a 50/50 mix of water and antifreeze boils at 223°F (106.1C). Radiator cap pressure designations are usually advertised in bar, with most stock radiator caps designed to withstand pressures up to 1.1 bar (16psi). The more pressure a fluid is under, the more difficult it becomes for the fluid to vaporize, and the higher its boiling point becomes. When water is under 1.1 bar of pressure, the temperature water will boil at is 260°F (127°C) while a 50/50 antifreeze mix will boil at 271°F (133°C). By installing a radiator cap designed to withstand higher pressures, an additional increase in the coolant’s boiling point will be seen. High pressure caps are usually designed to withstand 1.3 bar (19psi) of pressure. This 0.2 bar (3psi) increase in pressure over the stock system will increase the boiling point of water or antifreeze by 8.7°F (4.83°C). This will then bring the boiling point of pure water or a 50/50 antifreeze mix to approximately 269°F (132°C) and 280°F (138°C) respectively. While this small temperature increase alone won’t do a lot for your engine, coupling a high pressure cap and using coolants with better heat transfer properties can do wonders. Antifreeze (ethylene glycol) alone is not an inherently good conductor of heat. In fact, pure antifreeze conducts heat about half as well as water, while a 50/50 mix of antifreeze and water conducts heat approximately three quarters as efficiently as pure water. This means a cooling system using a 50/50 mix of antifreeze would have to flow faster than a cooling system filled with pure distilled water in order to achieve the same cooling efficiency. What this means for you is significant cooling gains can be made by using distilled water and an additive called “Water Wetter” in place of an antifreeze-water mix. Water Wetter is an additive that improves water’s “wetting” abilities (another whole subject), adds corrosion resistance, and slightly increases the boiling point of water. A high pressure radiator cap in conjunction with distilled water and Water Wetter as the coolant is by far the best route to go for high performance applications where freezing is not an issue. For applications which must still be resistant to freezing, the antifreeze-water ratio can be altered in favor of mixtures incorporating more water than antifreeze so that the cooling efficiency of the mixture is improved. Just bear in mind the freezing point of the mixture as it is thinned with water will be reduced, so you will need to pay close attention to the environment you are operating in so that the coolant is never susceptible to freezing. A frozen coolant system can ruin an engine and makes for a very bad day! I hope you enjoyed this post on three easy ways to improve your engine’s cooling. One more thing before I wrap up! April is Autism Awareness month, and here at DIY Moto Fix we couldn't be more excited to announce that we will be donating 15% of all profits made in April to AutismMX. If you haven't heard of AutismMX, this amazing non-profit brings Autism awareness to the motorcross community. Founder, Matthew Dalton, created this non-profit after finding that motorcross was an amazing way to connect with his autistic son. At DIY Moto Fix this non-profit also touches a chord with us. Our filmmaker and photographer, Kelsey Jorissen, loved dirt biking with her autistic brother throughout their childhood. The Autism MX Project focuses on four areas: Autism MX Day Camps are days for ASD kids and families to have the chance to ride AMX’s little dirt bikes and quads and enjoy the sport of motocross. Team Autism MX Sponsoring amateur MX racers, riders as well as sponsoring AMA pro racers. Through doing so, they are getting out the word on Autism Awareness to millions. AMX Puzzle Piece Apparel from shirts, graphics, goggles, to help stand out and support Autism Awareness. AMX Ride Days for Autism Awareness AMX celebrates Autism Awareness and is a fundraiser for The Autism MX Project. So for the entire month of April - if you buy a book, a video, even a poster - 15% of that purchase will go towards AutismMX and their amazing cause. Thanks for reading and have a great rest of your week!