I am putting a B31 engine into my WM20, as I want a bit more power and I like the look of BSA OHV singles.
My question is that the breather on the B31 engine is on the timing gear cover. Do I have to pipe that into the oil tank the same as the breather on the left hand side of the old sidevalve engine?
Cheers

email (option): gasboy@btinternet .com

Hi Peter, the breather located on the drive side of the crankcase was not originally routed to the oil tank...a length of copper pipe ran down behind the primary chain cases and deposited any oil on the road. Likewise with the timing cover breather...a shorter, but larger diameter, copper pipe went behind the exhaust pipe and terminated about level with the bottom edge of the gearbox mounting plates. Again just pointing down at the road...Ian

email (option): ian@wright52.plus.com

Thanks Ian-- I knew you would reply to my wail for help.
So on the B31 (a 1956 engine) there is no crankcase breather routed back to the oil tank?

email (option): gasboy@btinternet .com

That's right..it just lubricates the tarmac. Go for a post 48 timing cover (with the 'wing')..that has the later pattern 'shroud' cast into the casing to prevent excessive oil loss from the breather. Use in conjunction with the later breather assembly as well...this has the inner end of the breather pipe pressed flat and a small exit hole drilled through the side...Ian

email (option): ian@wright52.plus.com

Hi Peter.

The link back into the oil tank was done in order to save the drop of oil back into the tank as a modification in some bikes.

As Ian said- it should be pointed down, usually on the chain, lubricating it while dropping.

Noam.

email (option): noam10@gmail.com