[VicYouel]

Hi Ian and glad to see you are out  riding. Oil is meant to go up the push rod tubes to provide an oil mist to valves and rocker shafts. However as John states when the piston/rings wear the crankcase pressure will increase and over oiling will be the result. In the Vincent world there have been many dialogues on crankcase pressure and breathers; one thing that did make sense to me is that with these flap valves  the crankcase pressure probably sits at 2 psi below atmosheric pressure in normal running conditions.  Model 9's for 1932 onwards provided a better rocker lubrication but 90's had further adjustable feeds.

[singleminded]

On my bike the breather runs from the timing chest which is where the push rod tubs fit, so yes air will go up the pushrod tubes..You have to think about breathers though, they do most of their work when you are kicking the bike over. As the revs rise they become almost ineffective as the air is trying to flow and reverse so fast that almost no air movement occurs..till the rings wear out and you get too much crankcase pressure that can't be relieved and massive leaks result---dribble dribble, a bit like me..john

[Iansmart]

My Model 9 has no lubrication to the top-end, but there is considerable pressure in the rocker box! A rocker box bolt fell out on a 'brisk' run and when I stopped I noticed air blowing out the bolt-hole. I wonder how it got up there? i have the usual disk flap on the crank case which appears to be fine. I can't blow into it, but I can suck. Could it be going up the push rod tubes?