RD 350 LC Gearbox sticks in 5th gear when hot

[500comet]

My RD 350 sticks in 5th gear when hot after a long run and is OK when the bike is allowed to cool a bit.

Have taken it to pieces and can not find anything wrong.  Anybody any ideas what the problem might be please.

Matty

[billy]

I had this kind of problem on my LC (which more or less uses the same gearbox as YPVS, only difference is driveshaft and shift drum lengths I believe), the gear lever would start jamming after shifting (usually when shifting up), so I had to push it back down with my foot.

I noticed the problem seemed to be directly related to the age of the gearbox oil. I don't know how many miles it took until the problem started occurring, but I'd say roughly after 10-15 km (km, not miles), which is pretty much nothing.

BUT...

There is a way to fix it. Cut that stupid original shift star down to releave some of that tension of the detent arm spring and shift drum assembly.

I never did it to prevent the jamming gear lever, but rather because I hoped it would make the shifts feel a bit smoother, and also finding neutral a little easier (cant say I noticed a major difference though).
The non-jamming gear lever was just a well appreciated surprise. It never ONCE jammed when I used my cut-down shift star. When I put an original shift star back on, the jamming gear lever quickly started occurring again. Gah..

My modified shift star looked more or less exactly like the one on the picture below. The tips was cut down on a bench grinder and rounded off (obviously not the area between 1st and 2nd gear, and between 6th and 1st gear as you can't go from 6th to 1st anyway). I used a file and some wet&dry to do the final finish work. Overall it was much easier than I expected it to be. A 5 year old could do it.



Don't forget to use loctite on the screw that holds the shift star to the shift drum, as you'll have to remove it in order to perform this modification.

[500comet]

Thanks for the advice. Yes the gearbox is in pieces on the bench and it all looks OK.

However it was down to about one third full, having been filled only a short time ago.
There were traces of a thick oil in the crankcase so we believe the seal between the crankcase and gearbox had leaked and hence the gear oil had been burnt in the engine.

Crankcase will be re assembled using some very expensive non silicon commercial sealant used on agricultural machines - it costs about £60 for a small tube and we hope this will do the trick and keep the gearbox oil in and that the problem was largely due to low oil in the gearbox. Most of the gearbox bearings and seals have also been replaced, so will update this thread when some testing has been done.

[kevsypvs]

yes three bond as above its very good and cheap ive used it on rebuilding various engines and never had any probs with it , hope you get it sorted mate