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Found 10 results

  1. Hello all, I recently picked up a 1978 Yamaha IT175 off of Craigslist that needed a ring. Instead of doing just the ring, I have ordered a new piston and ring and am going to replace both. I have never worked on a 2 stroke this old before and have never done a top end on any bike before, so I was wondering if anyone could put me in the direction of an instruction sheet for the top end on this bike as well as some tip and tricks for general stuff. Also, if anyone has first hand experience with a similar bike, that would be awesome! Thank you all in advance!
  2. bianco013

    97 CR125 bore size

    NOT ANOTHER BIG BORE QUESTION!!! Ok, ive searched high and low but cant seem to find concrete answers. I have a 97 Cr125 that been sleeved and bored twice over already. i blew the top end at the end of summer and am getting around to the maintenance. I plan on sending the top end into Millennium Technologies to have it bored out and the powervalves gone through. My question is... how big can i go? I have found a 56mm overbore kit on ebay.. will this be too big? its cheaper to buy thr rebuild kit myself and just send them the top end for machine workThanks for the read and the help
  3. Paul Olesen

    New and Re-plated Cylinder Prep

    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
  4. 1994 Wr250z

    Can I use this piston??

    Hey everyone! this is my first time doing a top end rebuild. I pulled the head off and the old piston has a “B” on it and it says 67.95. The service manual says the piston to wall clearance should be .04mm. I just bought a set of feeler gauges. If I measure the clearance and it is within .04 , should I buy a 67.95mm piston? If so.. what kind? I have attached some pictures of the piston in it and the pics of the cylinder.. keep in mind.. my cylinder doesn’t have anything stamped on it.. must be worn off. Thanks for any help!!
  5. I've been doing research over week now. Bought a 04 crf250r for $900 on terms it needed a cam chain. Come to find out the cam chain tension failed and the chain was shot. However there was a surprise. the left cam lobe closes to the cam wheel (in the head) destroyed the heads housing around the valve. Yes destroyed. Chucks of metal were found and the cap above the valve (under the cam lobe) was also destroyed and chewed up. The bike did run before i opened it decently well but did make noise (2nd 3rd kick). I didn't want to blow it up so i torn it apart. Now i have a new cam chain and tension valve cover gasket and flywheel stator (left side engine gasket) also new head is on its way. PROBLEM- Guys at the motorsports store said valves looked good and jug looked fine along with the piston (valves were still in head and he just glanced at them). QUESTION-Do i reuse the old valves in my new head (probably not) so if i order new valves can i use the old springs with the new valves? Last question, since ill have a new head and (if need be valves,springs,locks,seals) what size shim (referring to the small metal circles under the lifters) do i use since it'll be OEM. Please get back with me asap. Thank you!!
  6. I have 4 xr200's i have accumulated that need rebuilds,pretty much top ends,rings,valves etc. T was wondering if the 75 dollar kits on fleabay fit these bikes. It looks like they have a hole in side for chain tensioner,similar to crf230 engines. Could i just put a 230 cam chain tensioner on one and use it? I dont usually[ever] go this cheap route but they are like rabbits,they keep reproducing or something,they are in my way constantly.most are decent bikes and worth to get running decently and sell reasonably,and dont want to sell anyone a time bomb either. Anyone gone this route?
  7. Guy Robinson

    Xr250r 1998 head

    I may be being a bit of a moron so forgive me :-) Stripped down top end on an old xr250 1998 i haven't done this kind of rebuild before but took the plunge anyway All stripped down and starting to clean all the parts up before rebuilding cam out .. all good until I tipped over the top of cylinder head ( part with valves in it ) and a little spring fell out ? Only maybe 4mm wide by 15-20 mm long ? I think I have found a hole it came from. It nonidea what it is or if I have definitely got it in the right spot ?
  8. 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
  9. hey guys just picked up a new project bike. Its a 2008 Yz450f with a big bore kit and a stroker crank. The total cc of the engine is now 499. It runs on race gas and will be an absolute monster when shes ready to rip. I will continue to make more videos on the bike so stay tuned Link to the video:
  10. Hello folks, I'm a new member in this forum and need some advice here. I purchased a new to me 2005 crf250x and first thing I did was check the valve clearance. In: L=0.005" and R<0.0015" Ex: L=0.011" and R=0.011" The manual says valve clearance spec is 0.005" +- 0.001" for in and 0.011" +- 0.001" for ex. So everything is in spec with the exception of Right Input. This is my first dirt bike and dirt riding is new to me; I'm only expecting to ride slow woods/trails. Should I try to shim it and continue riding? Have already hot cams shim kit should be coming in soon. OR Should I do a top end rebuild? As for the rebuild, I'm thinking about putting new valves, valve guides, valve springs and potentially changing the piston (rings and pins too). I saw some posts here about rebuilds, planning to do it myself mostly other than the pieces that require machine shop intervention. What are the items I will need to get done at the machine shop - I do not have the slightest clue, any pointers will help. Also, I'm located in North Atlanta, GA - I would appreciate if any local riders has any local machine shops that specializes in dirt bike heads. Thank you!
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