My JAPs have a timed breather almost identical in action to the Vincent one, they also have NO crank seal arrangement, literally there is a single open ball or roller bearing and the mainshaft comes out through the casing.
Interesting they don't leak either, the valve is timed to open 90 degrees before BDC of the crankpin whether it's a single, 50 degree or 60 degree twin, total loss or recirculating.
You can tell if you've got it wrong, you get oil coming out everywhere !!
I have checked the duration of the opening, 90 degrees, so it closes at BDC and is a 3/4" long slot
Interesting they don't leak either, the valve is timed to open 90 degrees before BDC of the crankpin whether it's a single, 50 degree or 60 degree twin, total loss or recirculating.
You can tell if you've got it wrong, you get oil coming out everywhere !!
I have checked the duration of the opening, 90 degrees, so it closes at BDC and is a 3/4" long slot
Last edited: