leaking V50 gearbox breather

I have 2 v50 mk2s and both of them are leaking gear oil from the gearbox breather located on top of the gearbox, any ideas on how to sort this? cheers Chris.

Are you sure it is g/box oil (a sniff should confirm it)? Typically they do leak engine oil from the air filter unit where the engine breather runs in to it – especially if you fill beyond the half way point on the stick. That oil then all sits on top of the box.

What does a V50 gearbox breather look like?

E.g. does it have hose…

Its definitely gearbox oil, the breather looks like the type you would get on an industrial motor gearbox, it has a top hat shroud on the top of it. The conventional air filter system has been removed and the engine breathers have been modified to suit this setup which is working perfectly.
Any way I think I have sorted this problem now as I have just bought a spare v50 gearbox which someone has done a breather mod to, so I think ill do the same.

OK - Understood. I have never seen a problem with the V50 g/box breather decanting previously - and I have worked on a few. Certainly never considered a mod to be necessary. Could you post on here what that looks like.


Daft question time ~ not simply a case of being overfilled (wrong quantity) ?

all 3 v35/50/65 i have had do the same

, gently blow about 100ml of ep80/90 out then settle down

… factory spec was altered to reduce the 1l down to 900ml to reduce the problem. only way i have sorted is to drill a 4mm hole in the top of the breather ( off the bike) and attach a length of hose to it.

Note the breather holds the detent spring so don’t move the bike or start it until the breather is screwed back in

i’m pretty sure this is what has been done to my spare gearbox, I will look into it a bit more later.
cheers Chris.


Stick to 1litre and enjoy 100ml of rust protection