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Paul Olesen

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About Paul Olesen

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

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  1. Thanks for your support, I hope you enjoy the book! Thanks for your support!
  2. In today's post, I'm very excited to share details about my new book,The Two Stroke Dirt Bike Engine Building Handbook. As with all of my blogs and technical resources, my goal has been to bring riders clear and concise technical information. My two-stroke book exemplifies this and puts nearly 300 pages of engine building knowledge at your fingertips. I wroteThe Two Stroke Dirt Bike Engine Building Handbook to be an all-encompassing guide on engine building. From the moment there is doubt about the engine's overall condition to the time the rebuilt engine is broken in, I give you a step-by-step guide to help you work towards a successful build. My aim was to create a definitive resource that hit on all the relevant topics you'll encounter as you proceed through an engine build and take any guesswork out of the equation. Throughout the book, engineering knowledge and practical experience are fused together to detail the how and why behind the way procedures are performed, parts are designed, and engine performance is affected. This is the most important and valuable aspect of the book, and it's something you won't find in a service manual. The book doesn't just tell you to bolt part A to part B, it teaches and explains the correct way assembly procedures should be performed and why it is necessary to do so. It also explains the intricate relationship between parts, where to look for wear patterns, and shows examples of worn and damaged components. If you're interested in making modifications to your engine or if you're curious about how certain modifications affect performance, I wrote an entire chapter dedicated to the subject. Within this chapter a discussion on how performance parts such as expansion chambers, port timing modifications, and cylinder heads alter overall engine performance is included and helpful suggestions are provided to aid you in choosing the correct components for your build, depending on your specific riding needs. If you have a thirst to learn more about how your engine works and a desire to correctly disassemble or assemble an engine to professional standards, you will benefit greatly from this book. Whether a complete beginner or a seasoned builder, with nearly 300 pages and 250 images worth of information, there is fresh and useful knowledge for everyone. There is also valuable material packed into this handbook that doesn't just pertain to the act of building the engine. I include instruction on diagnosing engine problems, sourcing and determining which parts to replace, using precision measuring tools, setting up your workshop, and additional tests and inspections that should be performed when preparing racing engines. If you just want to build your engine back up to stock spec, you are covered. If you want to go the extra mile and prepare a racing engine, you are also covered. In a way, this book allows you to choose your own ending by giving you all the tools and knowledge you need to complete your build at whatever level you decide. As a way to thank you for your support, we're offering TT members 15% off during a special TT pre-sale which runs from now until December 5th (when the book officially launches). Simply follow this link to learn more and order: ThumperTalk Pre-Sale Thanks again for all your support as we've grown DIY Moto Fix from an idea to a thriving community of riders who are passionate about making their machines perform better through their own hard work. Thanks for reading and have a great week. -Paul
  3. Happy Birthday ya old dog! ;)
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    1. Paul Olesen

      Paul Olesen

      Thanks Bryan!

  4. Hi Scott, thanks for picking up a copy of my book! It's great to hear the booking is helping you out.
  5. Hi Jakob, Our book is not distributed to any physical stores, however, it is available through our website and we ship internationally. Paul
  6. In my last post, I shared details about how the two-stroke cylinder works, in today's post I want to provide an overview of how a performance two-stroke engine's exhaust system works. Adding a performance exhaust system can be a great way to increase power and/or alter the power delivery of an engine. I would also argue that optimizing a two-stroke engine’s exhaust system is equally as important as ensuring the cylinder’s ports are correctly designed for the given application. Not all exhaust systems are designed to do the same things, and much like cylinder port design, exhaust designs are intended to alter power in specific ways. Having a basic understanding of how an exhaust system works can go a long way when it comes to selecting the right exhaust pipe for your engine. Two-stroke exhaust design is complicated and there are many different variables that must be considered when designing a pipe. I don’t intend to go into all of them, but I will share a few of the most critical. Each time the exhaust port opens to release spent combustion gases, pressure pulses are created. Modern pipe designs harness this pulse energy and use it to help scavenge and fill the cylinder. The process starts when a positive pressure pulse is created once the exhaust port opens and combustion gases leave the cylinder. The positive pulse travels down the pipe until it reaches the diffuser, at which point part of the pulse is inverted and reflected back towards the cylinder as a negative wave. This negative wave is very beneficial in pulling spent exhaust gases out of the cylinder and fresh mixture up through the transfer ports. The remaining positive pulse continues on its journey towards the end of the pipe where it encounters the reflector. The reflector acts as the name implies and forces the positive pulse back towards the exhaust port. Once reflected back, the pulse remains positive and, if the pipe is designed correctly, will reach the exhaust port just as the piston is about to close off the port on the compression stroke at the desired RPM for maximum power. Any fresh mixture which has escaped out the cylinder will be forced back in by the positive pressure pulse. The tuned length of the pipe is dictated by the exhaust port timing, RPM of max power, and the speed of sound. Pulse length and amplitude are governed by the angles of the diffuser and reflector. Generally, steeper cone angles create pulses with more amplitude but shorter duration. Shallower angles generate pulses with less amplitude but longer duration. Given these variables, it is easy to see how a pipe could be tailored for specific applications. An engine converted for road racing may utilize a pipe designed for peak power which incorporates steep diffuser and reflector cone angles so that pulse amplitude is not sacrificed. This peak power would likely come at the expense of a narrowed range of power. An engine tailored for woods riding may feature a pipe with shallower cone angles, resulting in less pulse amplitude, but a broader spread of power. The last parameter I want to touch on is how the tailpipe, which is sometimes referred to as the stinger, influences the pipe. The tailpipe creates a flow restriction in the pipe which allows the pipe to have a certain amount of back pressure. Enlarge the tailpipe and the back pressure decreases, make it smaller and the back pressure increases. As back pressure increases or decreases, so does temperature and ultimately the speed of sound. As the speed of sound changes, so does the resonance RPM of the pipe. If the tailpipe is sized too small, cylinder scavenging will be inhibited. When this happens, the cylinder, fresh mixture, and piston will all be overheated. While engineers and tuners can estimate starting pipe dimensions and tuned lengths, a great deal of trial and error testing is usually still necessary to fine tune the exhaust pipe and optimize the design. Unless you intend on building your own exhausts, this work will have already been done for you. When selecting an exhaust system, you need to focus on how the exhaust alters the power curve. Exhaust systems are tailored to deliver more bottom end performance, top-end performance, or performance throughout the power curve. Selecting which system is right for you will depend on how you want your engine to perform. If you’ve chosen to modify your cylinder ports, installing an exhaust system that compliments the porting can be very beneficial. You might be wondering about slip-on mufflers. If you’ve followed along with my explanation of how exhaust pipes work, you’ll notice I made no mention of the muffler. While the muffler can have a small effect on performance, it is not the primary factor. Upgrading a muffler is a good way to reduce weight, but there won’t be a slip-on out there which significantly increases power, in the same way, a properly designed expansion chamber can. I hope you enjoyed this write-up on key features affecting the performance of two-stroke cylinders. As for Two Stroke Handbook news, we received our first printed proof of the book this week! Needless to say, we are inching closer and closer to an official release date. To stay updated on The Two Stroke Dirt Bike Engine Building Handbook we created an email sign up for our readers. Click this link to sign up, 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
  7. You're welcome, I'm glad you enjoyed the article.
  8. 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
  9. 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.
  10. 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.
  11. 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.
  12. 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
  13. 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.