5th gear trouble--GZ250

[Messinupthegarage]

I recently bought a salvage GZ250 with light body damage but bad 5th gear--wanted a challenging project. First, the bike has 400 miles on it, starts and runs great. In 5th gear, about 45 miles an hour it will rev and the bike will slow then catch up wth the engine and speed up again. It does not buck like the gear is too tall and I can keep it from happening by applying constant upward pressure on the shifter. I re-adjusted the clutch, adjusted the valve clearance, spark plug gap, replaced the air filter and replaced the cam stopper spring(had to have one made as they no longer make them) and still keeps happening

I have the service manual and have torn the cases apart and checked the shifter shaft, shifting forks--they are all spec, not bent or worn. The only problem I can find are some very slight wear on the dogs on 5th drive gear. The groove for the fork in this gear is a tiny bit out of spec-- 0.172-0.173 inches in a few spots and the upper limit of normal is 0.171. No visible damage has been done to any part of the tranny otherwise. The spacer washers for 5th gear are also thin by a thousandth of an inch. I want to know if this tiny problem is enough to translate into transiently slipping in and out of gear and should I order a new 5th drive gear and washers. Are there any other tricks to try?

try pushing on the gear and see if you can move it to the point that it would pop out of gear

check the shift drum .some times the little cam grooves chip away