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About AV8R

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    TT Silver Member

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    South Dakota
  1. AV8R

    piston break in

    If you use a cast piston ie OEM, then heat cycles are of no use. Simply get it up to temp varying the throttel constantly and ride it like normal. Most of all DO NOT baby it, ride it hard. The rings have a very small widow to seat, after a very few minutes that's it they are seated and the compression they achieve will be it until the next top end. This is all assuming you roughed up the cylinder by ball honing or cleaning out the aluminum build up in the cylinder before re-assembly. Now if you have a forged piston ie Wiseco, then heat cycles would be a good idea to get the piston to conform to the cylinder without creating significant rub spots. Warm it up until the radiators are hot to the touch by varying the throttle constantly and then let engine cool to ambient temp (at least one hour) then do this again and let cool again. On the third time let it warm up varying throttle constanty then go ride the bike just below the pipe for 10-20 minutes lugging the engine the whole time any time you cannot lug the engine pull in the cluch and vary the throttle like you did during the warm-up then back to loading the engine. Loading is important to create the pressure necessary for the rings to seat well. Let it cool again. Then ride it like you stole it. I personally always did a dry install on the top ends and never and I mean never had a blowby issue with my top ends. They always achieved good compression and lasted a long time (65-75hrs of motocross use). Just remember the first time you kick over the engine fuel is supplied to the piston, with that fuel comes lubrication (pre-mix). So your piston is never without lubrication even when it first starts after a dry installation.
  2. AV8R

    do i need to replace crankcase?

    Are you saying the main bearings spun inside the case? If new main bearings are still tight in the case, i.e. have to be tapped in, then I would say you are ok to go.
  3. AV8R

    squish and detonation OH MY!

    Try putting a couple of copper washers under the spark plug. That will recess the plug slightly in the head creating more space for combustion and lowering the compression... maybe enough to eliminate detonation.
  4. AV8R

    Oil question for the mechanics!

    I would have to agree with this statement. Due to your last slow puttering ride your reading is not represenative of your average riding. I would leave it alone unless your coming up dry in that test.
  5. AV8R

    Leak Down Test - Need Guidance

    You can test it on the bench or before you run it. It's just that you may note "some" leakage. This can be verified by using soapy water in a squirt bottle to visually see where it is leaking from. It will be very slow and will stop at some point prior to leaking down to zero psi. As far as the powervalve vent goes, think about it for a second and you'll see that obviously you need to plug that vent. It is a direct line into the cylinder via the powervalve assembly.
  6. AV8R

    Clutch lever is really wearing me out!

    A worn out clutch basket or one with even slight grooves makes the clutch pull much harder.
  7. AV8R

    Leak Down Test - Need Guidance

    On my bike the base gasket (which is paper) would leak until it runs. My guess is that the premix gets into the gasket and seals it up. The head o-rings leak sometimes until it's ran also.
  8. AV8R

    Leak Down Test - Need Guidance

    On my bike the base gasket (which is paper) would leak until it runs. My guess is that the premix gets into the gasket and seals it up. The head o-rings leak somtimes until it's ran also.
  9. AV8R

    Leak Down Test - Need Guidance

    Yes, you have to plug the powervalve breather. You may find that the engine will not hold pressure perfectly right after rebuild. It may need to be run a couple times.
  10. AV8R

    YZ Suspension questions

    I tried the spring loaded bleeders and found that they leak sometimes, meaning they breath and if it is sucking in air then it is sucking in dust. I would go to relieve the pressure and one would fork would have pressure in it while the other one would not. So I decided not to use them.
  11. AV8R

    removing swing arm bolt ?

    If you mushroomed the end then you'll need to file the mushroomed part down until it is the same diameter as the sourounding area on the bolt. If you don't then verrry hard to get through and likely more mushrooming in the process.
  12. AV8R

    Odd blowby on cylinder

    Looking at the piston on the left(1st pic) and then the one on the right (2nd pic) it looks like the bottom of the skirt is bent in. Is this an illusion or is it really bent? Tons of blowby on that second piston definately a problem there.
  13. AV8R

    250 running strange after rebuild

    One thing caught my attention in your explanation of all you've done so far, and that is that it kicked back while trying to start. That usually indicates a timing issue. It would be coincidental that your timing went off somehow during your topend overhaul but who knows strange things happen some times. Pull off the flywheel and check the woodruff key. if it is damaged then there is your problem. It is quite odd that it changes pitch or sound-wise for no apparent reason. A flywheel that rotates a little on the crank shaft could explain this. Also a loose stator (the stationary coils behind the flywheel) could cause this so check that as well. One other thing that affects timing is the TPS on the carb (I believe) test that per the manual and see if it is operating correctly. Then you've eliminated everything timing wise other than the CDI. Hope you find something as this is getting to be quite a challenge to diagnose.
  14. AV8R

    250 running strange after rebuild

    I must have stuttered.
  15. AV8R

    250 running strange after rebuild

    Right. I was just thinking that maybe he removed the piston from the con rod to clean it up or some such thing. Then perhaps re-installed it facing the wrong way.