Ariel Owners Motorcycle Club

Hi i have a 1936 Ariel vb600 after starting despite good scavenge back to the tank i get excessive amounts of oil in the outer timing cover .it eventually leaks out of the lower breather and magdyno shaft seal . i have good oil pressure and i have replaced the balls and springs in the pump after many years of Ariel ownership i am stumped with this as i don't have this issue with my other singles . Any ideas as to the cause would be welcome ?

Sounds familiar. Pre-38 timing cases have the oil drain holes much higher than later engines. This is my 37 inner timing cover: There are also correspondingly higher drain holes in the crankcase. Do you have the higher drain holes? Later covers have just one drain hole much lower.

It makes a big difference how far the lower breather elbow is screwed in. If it's flush with the inner cover, a lot of oil will leak out; more surprisingly, if it's too close close to the chain, it will also leak more oil.

Do you use a later oil pump with the bigger delivery piston? If I fit a later oil pump, I leave a trail of oil drops. I have switched from SAE50 to SAE40 oil, which seems to help with the oil in the timing case. Having said that, more oil leaks past the piston rings. On my 100mls journey to the Ariel rally, I used about half a litre of oil at 35 Celsius and traffic jams in Gloucester! Normally it's much less.

I asked people with pre-38 bikes whose bikes don't leave a puddle of oil behind. Usually they had blanked off their lower breather in the chain case.