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smdonald

YZF Transmission

15 posts in this topic

Hey guys. I have an 01 YZ 426F. Bought it about 1 month ago. It ran beautiful for the first few weeks. Had it at the track and on the trails. No problems. I put about 12 hours on it and changed the oil 3 times. Last week while on the track, it just seized up. I tore apart the top end and found out that was fine. Then proceeded to tear down the rest of the way. When i got the clutch and basket off, the engine freed itself up. The crank, top end, and all the basics are fine. The oil filter is covered in metal. Im going to split the case all the way down because no doubt its the tranny. I was wondering what you think might have caused this, and if anyone has heard of this problem before. Let me know.

Thanks,

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I'm guessing it's 3rd gear....................I've heard a few that did that.

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I'm guessing it's 3rd as well. I had 3rd gear failures on my 01 yz250f twice. First time it happened, the chunks stuck to the flywheel stator causing it to shut down with no other damage. 2nd time, I just had a loud chattering sound in only 3rd and unfortunately a piece scored my cylinder. I noticed the 2nd time it happened, the new yamaha gear I ordered was designed differently. The older one had holes where the shift dogs ride. The new one, has a spot for the shift dogs, but there are no holes, it's filled. Maybe the new gear is refined and stronger? Either way, what a b*tch..... I don't like when things break..... twice. And isn't this ironic, I have 426 posts, and that is my first post I think ever in the 426 forum! :busted:

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thanks guys. Im tearing it down on Monday to reveal the culprit! Does anyone think i should replace all of the gears? Might make it more reliable in the future?

ive done all kinds of engine work but never a tranny. i have no experience in that field.

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I had twice a similar issue. But don´t care. First time it was my fault, i changed the broken gears and then i rode about 200h on the bike (426 01). Then my 3rd gear broke, but i was lucky both time it was like my clutch has been broken but it was a bend gear shift and the knobs on the gears were already round. I´m also not sure if the second time was my fault because about 10 hours before i fastenend my clutch nut trough the transmission with locking the rear wheel. maybe i bent then the shift fork a little and the riding made the rest.

So change the gears, the Yam is very reliable and ride it. When you are repairing it on your own, order the stuff at thumpertalk and it will cost you about 250 bucks. For about 200 or more hours of riding it is ok. Don´t forget you have bougt a race bike with great power in comparison to size and weight.

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Trying to complete the teardown. I have a clymer manual which has been useful. The only thing left holding me back from crackin this baby open is that the nut that holds on the drive spocket will not come off. Any ideas? The clutch and all is already off.

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Make a slot on each side of the nut with a small cutoff wheel , put the chain on and have someone hold the brake or use the wood through the spokes method.. use a cold chisel and hit it at an angle in one of the slots to spin it off.. you might want to try the wood with an impact first if you don't want to destroy your nut.

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The manual actually recommends placing a piece of wood or aluminum between the primary gears so the nut can be removed. If you don't have a strong enough impact wrench, set the clutch basket back in place and try that. Don't beat up the nut. :naughty:

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oh no, I'm in touble :banghead:

My nut wouldnt come off with a 1/2" impact @ 140 PSI and was bunged up a bit. I see cutting and tapping with a hammer as a reasonable solution since I don't have access to a 3/4" impact.. but yeah its probably not a good idea

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What do you mean place a piece of wood in between the primarys?
With the gears meshed, use a piece of hardwood wedged into the gears to prevent the crank from turning.

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Thanks. Will try tonight. After that is off I can split the case and discover what else is wrecked! Will report back.

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