Hi Garry,
quote Garry in Tampa:
You are all forgetting about the drain line from the top main bearing. Excessive gas/oil from their would indicate excessive bearing clearance. Plug up that line and the magneto gets flooded.
Can you cite anything in the literature which describes the function of that ‘drain’? I’ve looked at it while I’ve had motors apart, and I can’t see how mixture would ever accumulate outside of the case, above the main bearing and beneath the magneto.
I’ve always assumed it was part of the lubrication system – vacuum from the low-speed bore would pull mixture upward, into the helical grooves in the main bearing, to provide lubrication.
Otherwise, how would the upper main be lubricated? Gravity takes care of the lower, but the upper would need a little more help in that department, I’d think..? Or is the primary compression pressure enough to push mixture into that area?