2003 yz 450 4th gear problems

4 replies to this topic
  • the426master

Posted June 04, 2006 - 05:58 AM


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


Posted June 04, 2006 - 12:15 PM


Time to split the cases! Sounds like the gear dogs are worn and won't stay engaged.

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  • the426master

Posted June 14, 2006 - 12:45 PM


the shifting fork was loose and wobbly on the shaft that the fork slides on

  • yamasaki

Posted June 14, 2006 - 01:22 PM


the shifting fork was loose and wobbly on the shaft that the fork slides on

you mean the shift shaft that shifter bolts on to? i have my '03 cases split right now.. trying to picture what youre talking about so i can check mine.. :bonk:

  • grayracer513

Posted June 14, 2006 - 01:40 PM


None of the above...

Each shift fork is permanently assembled to its rail, and unless there is an extreme amount of wear in the cases at the rail pockets, that's a non-issue.

And, there are no syncros in a motorcycle gear box.

The problem is that the locking lugs, or dogs, on the sides of the two gears that engage 4th are worn, and no longer have any undercut on them. Because of that, instead of the applied load holding the gears together, they are forcing themselves apart. This will have more than likely bent or seriously worn the shift fork, which will aggravate the problem further. You need to split the cases and replace the 3rd and 4th pinion gears and shift fork 2.

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