A10 crank breather questions

MikeG

VIP MEMBER
Joined
May 31, 2012
Messages
1,241
Country flag
I fitted one of Jim Comstock's reed breathers to my 71 Commando and it made a world of difference in oil weeps and seeps. I'd like to do something similar to my A10. Has anybody tried a Mike XS valve or something like it? I considered an adaptation of a Comstock valve, but since the BSA rocker feed is off the return side of the pump I'm afraid it might cause problems?
Just wondering
 
Triton Thrasher said:
There's no real correlation between the rocker feed and what you do to the breather.
The Comstock breather returns almost as much oil to the tank as the pump does, Jim says he actually designed it for clearing a wet sumped engine without removing the drain plug.
 
I misunderstood.

Will you really copy the Commando breather position that caught oil thrown by the flywheel?
 
Unsure of how it could be done really, or if a Comstock type breather is the answer. I have also been thinking of hooking up a Mikes XS type valve to the timed breather and the one at the left hand end of the cam galley, but that would make for a lot of hose/tubing hanging off.
 
The camshaft timed breathers, in principle are good except the gas channels are too small at higher RPM to evacuate the crankcase pressure. For the A10 and A65 motors, there is a cavity inside the pushrod tunnel that connects to the crankcase. The simple and effective means to reduce crankcase gas pressure is to drill and tap a brass NPT or BSP hose connector to the rocker box inlet cover on the A10 and on top of the rocker cap (toward the rear) for the A65.
Fit a suitable hose, i.e. 1/4 or 5/16 depending on your installed hose connector. Run this hose up and over to the rear of the bike and its worthwhile to install a small K&N breather filter as well.
 
Back
Top