Oil leaking from Gearbox to Clutch

Norvil do a nut with a seal in it. it stops oil migrating down the clutch push rod .I have a look for part number for you 068844 it listed under clutch parts First check oil ;level and the breather hole i not blocked. I added a breath into gearbox shell 

The most common cause of this excess oil is the mainshaft oil seal being badly worn. In turn, the descending pistons then push oil vapour past the seal into the primary case and on the up-stroke begin sucking oil vapour through the gearbox shaft.  

If you check out gearbox drawings, the inner end of the G/Box main shaft opens out into the the actuator arm. This is outside of the main box and not really subject to whizzing gears throwing oil at it.  Also it is well above the G/Box oil level.

Several suppliers do the fancy seal for the clutch push rod but I would say that this is an expensive sticking plaster.  Whereas a new main shaft oil seal might be the cure. On my 650 Belt drive set-up, I have a ventilated case to aid cooling the pulleys and this also stops any bellows effect causing oil vapour to come through from the gearbox.

So if this is the cause. If Jonathan cleans the primary case out making it oil free. and rides about with the inspection cover off. The sucking will be cancelled out . as there is no vacuum to pull oil out of the gearbox If the seal is so worn you will see black engine oil.