AJS & Matchless Owners Club

I've been working on a 1950 500 twin, someone rebuilt it years ago, and ever since it's been dumping about half a pint of oil out the crankcase breather ON SHUTDOWN. Slightly odd... turn off bike and suddenly a big pool of oil forms underneath.

They never found a solution, so their fix was to route the breather into a bottle, and to try to remember to keep dumping the bottle back into the oil tank.

The pumps are NOT reversed, and return flow seems strong.

I started poking around... pulled out the pressure relief valve just in front of the oil inlet line... and it looks to me like there should be an o-ring on it. There is a groove near the end with no o-ring.

Could this potentially cause the oil-spillage symptom?

I'm sorry I can't help much with this as I've never had a twin earlier than 53, but on page 11 of the 51 parts list you'll find all the parts. http://archives.jampot.dk/book/Spares_l ... _twins.pdf I've looked in the '50 parts list and it seems different.
I can't understand how it works but it looks like you may be missing a few bits. Perhaps someone with an early twin might shed some light on the problem?
Dave.