426 5th gear

currently having a problem with 5th gear only on my 426, seemed like it was slipping out a 5th, split the cases nothing wrong, anybody have any ideas, yamaha told me it was the clutch, replaced it, same problem, there is only 15 hours max on this bike.

Look really close at the 5th gear pinion on the inside where the 3rd gear pinion engages it.

If either of these is slightly boogered up or radiused that is your problem.

It does not take much.

Also Yamaha suggests replacing shift forks that are scratched or discolored. If there is any sign of wear on your shift fork I would replace it as well.

I would rather pay a few hundred dollars in parts than have to split my cases twice.

There was also some rumor a while back of 5th gears being improperly heat treated. The engagement dogs must be cherry or it will pop out of fifth.

Also check the way the dogs on your new gears mesh, you may have to chamfer the corners, the other thing that causes much greif in this area is the #2 shift fork holes in the cases wear really badly due to the ill meshing 3rd and 4th pinion gears putting exsessive force on #2 shift fork while running in 4th gear, these holes can be repaired by a good engineer with a digital mill that can map out the holes to drill and sleeve them.

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