Shifter oil seal keeps popping out - CB350

[Tugboat]

Weirdest thing: the shifter oil seal on the CB350 keeps popping out after I ride around a bit. As far as I know there shouldn't be any pressure there, since the bottom end is open to atmosphere via the cam chain tunnel & the vent at the top. I've got a new seal to replace the old one with - just wondering if anybody had a clue as to why it's getting pushed out in the first place.

 

[2_DONE_THE_TON]

How old is the seal?maybe it shrunk and or dried out so slips out by heat and pressure inside the motor?

On my kz 400 the pushrod seal kept popping out cuz theresl was too much oil pressure.

 

[Sonreir]

Do a compression test. The breather exists because a small amount of blowby makes it past the piston rings and into the crankcase. When rings get worn, more gases make it into the case and the breather can't vent fast enough to relieve the pressure.

 

[Parkwood60]

I would suspect blowby too. My Cl450 used to do the same thing occasionally.