Leaking Oil....breather problem?

tatty500

Well Known and Active Forum User
Non-VOC Member
Avery,
My comet had (has) two annoying causes of this escape of oil on the back face of the inner primary chain case.
Firstly, the Burman clutch sprocket has several large holes in it. Untill the engine has run up to speed these holes (and the chain) move oil from the bottom to the top. When starting, between kicks (not that Comets aren't always first kick staters) some of this oil will run down the back of the sprocket and, upon encountereing the mianshaft, some oil can run around and along it and out.
There is also only a rudimentary gutter over the top of the mainshaft hole (slot) in the chaincase to force oil running down the inside of the case avay from the hole and hence exiting.
The second cause was due to neglect (greater than mine) in a previous life. A really slack or warn chain had been touching the case at the bottom, below the clutch sprocket. The chain sideplates had cut into the internal bosses that house the chaincase cover screw threads. In one case this was cut deep enough to just break through into the threaded hole alowing a leak from under the screw head.
Oh, nearly forgot. There is a very poor joint where the inner case fixes to the crankcase. The case has large cavities cast in which often hold oil for later release! Perhaps these filled when everything was full during the sumping.
Tatty500
 
Top