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A10 crank breather questions

A10 crank breather questions

Postby MikeG » Mon Oct 10, 2016 1:45 pm

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
71 Commando
71 Triumph Bonniville
60 BSA A10
2007 Suzuki Bandit
various other rolling junk

MikeG
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Re: A10 crank breather questions

Postby Triton Thrasher » Tue Oct 11, 2016 4:49 am

There's no real correlation between the rocker feed and what you do to the breather.
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Re: A10 crank breather questions

Postby MikeG » Tue Oct 11, 2016 7:40 am

Triton Thrasher wrote: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.
71 Commando
71 Triumph Bonniville
60 BSA A10
2007 Suzuki Bandit
various other rolling junk

MikeG
Posts: 341
Joined: Thu May 31, 2012 11:17 am
Location: New Hampshire

Re: A10 crank breather questions

Postby Triton Thrasher » Tue Oct 11, 2016 8:09 am

I misunderstood.

Will you really copy the Commando breather position that caught oil thrown by the flywheel?
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Re: A10 crank breather questions

Postby MikeG » Wed Oct 12, 2016 8:26 am

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.
71 Commando
71 Triumph Bonniville
60 BSA A10
2007 Suzuki Bandit
various other rolling junk

MikeG
Posts: 341
Joined: Thu May 31, 2012 11:17 am
Location: New Hampshire

Re: A10 crank breather questions

Postby ML » Mon Dec 26, 2016 7:38 pm

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.

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