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the426master

2003 yz 450 trany failure

6 posts in this topic

my friend just bought an 03 yz 450 and 4 th gear won't stay in gear it goes in and kicks back out and kicks back in has any one had this problem and if so what was it I have suspicions of shifting forks or the synchronizers

:applause:

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Sounds like a bent shift fork and, now, prob'ly rounded dogs/windows....you need a new fork and the dogs undercut.

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Sounds like a bent shift fork and, now, prob'ly rounded dogs/windows....you need a new fork and the dogs undercut.

I agree, will probably need to get 2 new gears as the dogs will be rounded off, you may be able to straighten the shift forks.

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I all ready split the cases the dogs are great the edge that you would think would be ground down to a chamfer was still square the original owner said it started doing this two months after he bought it so he parked it in his garage and bought a 2004 :excuseme:

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I all ready split the cases the dogs are great the edge that you would think would be ground down to a chamfer was still square the original owner said it started doing this two months after he bought it so he parked it in his garage and bought a 2004 :excuseme:

Then the dogs aren't engaging fully into the cutouts in the adjacent gear (2nd I think) so slip out under load, then catch again when you back off. I'm surprised the dogs aren't worn. You need to set it all up in the case half and see where the selector fork is holding the gear, it should be pushed all the way into the adjacent gear when it is in fourth (make sure it driving through fourth when you do this). If it's holding it out and hasn't got full engagement of the dogs, check the fork for wear and straightness. The wear pads should be in spec for thickness and exactly perpendicular to the shaft which runs through them. Look for wear on one side, suggesting the fork is pressuring the gear in one direction when it's running in fourth. It ain't easy to measure the straightness of the fork, I do it by placing it on a perfectly flat metal surface if it's machined, and measuring the distance from the wear pads to the surface. Both pads should be the same. If the surface of the fork contacting the flat metal is not machined, I make up a rod. exactly perpendicular to the flat surface and slide the fork over that. You can bend the forks back straight if they are not too worn.

The forks can get bent when you have an off, hit a rock with the gear lever or shift too hard with your foot.

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