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longerirons

loud sharp ping at high rpms in 00 yz426F

8 posts in this topic

Im hearing something in the motor cant tell from where exactly. Its like something slamming into the side of the case . Its not real pronounced at idle but when the rpms are up you can almost feel it . Its not constant though maybe once every 5 or 6 seconds.....any ideas ??? afraid to start it at this point do not want to damage anything.......worse

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This is the one that the kick start locks up on, right? You'd better get in behind the clutch and have a look before you blow something apart.

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O.k everything behind the clutch checked out, there was a small chip missing on one of the kick start gear teeth. checked out the valves again, o.k piston and cylinder, o.k I think I am going to have to split the case to check out in there, It doesnt seem to be coming from that low in the bike but I,m out of ideas... I started it up after the clutch and top end inspection and the crackel sound is still there but even louder and more frequent . I'm still up for more suggestions, Gray...you seem to be the authority on thumpers.

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What octane do you run? have you tried running higher octane just to eliminate deto?

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This is the one that the kick start locks up on, right?

Also the one prone to have a loose counter-balancer drive gear, when it is loose it does make some noise, but it is more persistent than the post describes.

But that may be worth a look, that gear is on the right side, and on the '00 models is secured w/ a key, whereas on all later models that gear is held on w/ splines (hmmm.....).

edit: wanted to add that when this gear gets loose it can over time cause the main nut on the (right) crank end to come loose (due to the constant to-and-fro play), in my case it ended up eating that tabbed lock washer, and these various pieces did some damage. At any rate I wouldn't rule this out, if there is any play between the counterbalance shaft and the crank then that key (and maybe the gear) is worn (and something bad is guaranteed to eventually happen). That loose connection could conceivably result in some out-of-phase engine noise.

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I have not split the case yet, but I have found that the connecting rod bearing has a large amount of play in it, causing the connecting rod to jam at the bottom of the stroke . could this cause the loud ping, crack, sound I'm hearing, by letting the piston fly up a few mm higher in the stroke because of the bad bearing????

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If the piston has been hitting the head, there will be a cleaned off, bright area on both parts to indicate this. If not, it hasn't been. But it sound like the rod bearing roller cage has broken, which can let the rollers act more like brakes than a bearing. The noise you heard may well have been the piston being slapped against the bore as the rod tried to lock up. You should plan on replacing it, but you dodged a bullet.

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Also the one prone to have a loose counter-balancer drive gear, when it is loose it does make some noise, but it is more persistent than the post describes.

But that may be worth a look, that gear is on the right side, and on the '00 models is secured w/ a key, whereas on all later models that gear is held on w/ splines (hmmm.....).

edit: wanted to add that when this gear gets loose it can over time cause the main nut on the (right) crank end to come loose (due to the constant to-and-fro play), in my case it ended up eating that tabbed lock washer, and these various pieces did some damage. At any rate I wouldn't rule this out, if there is any play between the counterbalance shaft and the crank then that key (and maybe the gear) is worn (and something bad is guaranteed to eventually happen). That loose connection could conceivably result in some out-of-phase engine noise.

This happened to my '00 426. It made a bad knocking sound like you descibe. Its real easy to take the right case cover off, bend the washer off the nut and tighten it. Even if its slightly loose, it will cause a commotion. I had to do this twice over a six year period of owning the bike. Very common problem on this year YZ426.

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