Hi, Has anyone got a sketch, drawing or explanation of what causes this breather to release pressure. There is the breather pipe in the N/S rear top corner of the crankcase, adjacent to the primary chaincase, but which relief valve controls the pressure? Where is this breather outflow from? I can't find any sections for this particular area. I think the answer must lie in Service Sheet 202 but having read it a few times I can't see it. There must be a relief valve somewhere because air cannot be blown into the breather, even with the barrel off. Having got the barrel off and engine out while I sort out the gearbox grub screw, this is a good time to study this breather operation. There is a hole into the casing at the end of the cam shaft but this seems to be for the cam shaft, see pic. Any info on this would be very welcome. Thanks for reading.
The breather valve is driven from the camshaft pinion, it looks a bit like a top hat. A cork disc sits between the 2 to ensure no leak or cam float. Valve rotates and opens at the appropriate place to allow engine to breath, pressure passes through the top hat into a drilling in the inner timing cover then through the rib in cam trough in the crankcase to the breather port.
Photo shows breather valve in position.
Second shows drilling in crankcase.
Photo shows drillings in breather valve and inner timing cover.
Thanks Julian, it is not an easy area to pick up but I think I am getting there. I also now have a full version of Service Sheet 202 from Phil Bull so that also helps.