559 gearbox problem

Dear people, i am from Holland, and my 559 has a problem no one over here can answer to.
It slips out of 3rd gear when accellerating fast. I removed the left hand cover and clutch and found out both gearbox axles have much play, you can move them in and out.
The ball bearing of the main shaft ismoving along in the casing.
So
i suppose i have to add shims, but on which side of both axles?
Should the ball bearing be located against the circlip or more inwards?
Would be gratefull for some tips.
Best regards
Arnaud from Holland

Hello Arnaud, your problem is common problem. There are worn gears. Also you have too much free play of bearings. They should be tight in position. Their position should be on their stop in position in casing, so I think it's more inwards. You should put new bearings and use loctite bearing loc. Also you need new gears, you have worn third gear inside. Gears aren't problem to get here, older, but good. Also I can recommend new shifting forks and springs in mechanism. It's also commont problem of older JAWA.