- Jan 17, 2020
You point at the right problem , having the sump filled=excessive pressure on crankshaft oil seal and oil passing in the primary and even in trans,if left unattended. No reed valves or whathever breather system will prevent that. I can,t imagine so many riders have not understood this yet!!!There is another wet sump solution I'm considering that's easier and cheaper. But first I want to bounce the following assumptions off everyone.
If the oil drains into the sump down to the oil tank screen it doesn't really matter because the crank journals will dip into the oil until the oil psi builds up after a few seconds (there will probably be some leftover oil in the oil pump anyway).
Using a breather at the rear of the sump may help blow the oil into the oil tank quicker (but the sump will still be swamped the 1st few revolutions). See photo below.
The only real problem with wet sumping is the danger of blowing out the main oil seal at the PTO shaft.
Preventing the main oil seal from blowing out takes care of the problem and the excess sump oil will simply pump back into the oil tank - the same as all Nortons have been doing since the beginning.
A means of securing the oil seal should dissipate all "Norton head" worries (or not?).
A rear sump breather as shown below does empty the sump oil back to the tank more quickly - but the sump is still full of oil for a few seconds anyway so it really doesn't make much difference. The reed valve is there to reduce pressure and prevent oil leaks - it won't prevent the main oil seal from blowing out because internal pressure is still high until the sump empties (the crank is splashing into the oil) - and the reed valve breather can't empty the sump right away.