Oil leak behind clutch - 1959 G12

[Charles.]

Is it normal for a quantity of chain case oil to run out from the hole at the back of the clutch under normal circumstances? How critical is the oil level in the chain case? Can any form of seal be fitted to seal the chain case/gearbox shaft hole?

[Adrian Pancaldi]

Hi Michael, There is a specified amount of oil for the primary , I have lent my manual out so can't look it up right now. Too much oil will cause the problem you described, too little will fatigue and over heat the chain and it will eventually break with an aerating effect! If you were filling it by eye , with the primary chain at the correct tension , the bottom of the chain should just be sitting in oil at the inspection hole. I haven't experienced the problem you described on my G12 and don't think it's normal. That being said, I did have a inner primary (i'm not sure if I still do) that has been modified with a seal. If you are putting in the right amount of oil the things to check are; that the plate that fits over the shaft has no damage around the hole and that it doesn't move too freely, check that your engine doesn't have a crancase breathing problem or an oilpump scavenging problem,as both these will let too much oil into the cases.
I hope this helps you
Adrian

[Charles.]

Adrian,
Thank you for your reply, I shall try lowering the chain case oil level and remove the clutch to check the size of the hole in the rear case.

I will also look for a way of sealing the hole.

Micheal

[Eric]

The information that Adrian has given is correct, with the machine on its centre stand the oil level in the primary chaincase should be just enough to allow the lower edge of the chain to dip in it. However if the bike is left for a period the the oil will drain down from the main oil tank then fill the crankcase untill it reaches the crankshaft then overflow into the chaincase with oil at this level it will come out of the rear of the case around the clutch shaft hope this helps.