Hello. Gearbox oil is somehow getting into the primary chaincase of my 99. Has anyone any ideas why?
I have read of excess oil…
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Drill a tiny hole in the Box…
Drill a tiny hole in the Box inspection cover,(or clear the one thats there) . Fit the O ring oil seal special clutch nut sold by Norton spares stockists. Park your bike on the centerstand ,not the sidestand. Check oil level is just below level plug.Even better!, fit a side stand to the offside of the bike , great when the camber is wrong and would drain the oil away from clutch. I am up for that too , anyone done this ?apart from the Vincent?.
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Crankcase Breather
The main cause of gearbox oil arriving inside the primary cover is generally due to a very worn Crankshaft Oil Seal. As the engine pistons rise and fall, this allows a bellows effect inside the primary cover which in turn sucks oil vapour through the gearbox mainshaft.
Another possible cause is a loose bolt(s) by the front sprocket also allowing the pistons to push / pull oil vapour around the various innards.
Various third parties sell expensive oil seal kits to fit on the G/B mainshaft. Try renewing the crankshaft oil seal first.
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Gear oil in chain case
Thanks to you all who responded to my query and for the interesting answers. I've recently fitted a belt drive together with new engine main bearings and seals, so that's how I have noticed this problem. It's probably always happened but got mixed with the chain case oil and leaked out anyway. Also, the gearbox always dribbled from the k/s seal so over time, lowered the level too. the gearbox has new seals too now so I'll lower the level a bit. Wee hole in cap is clear.
Love the r/h centre stand idea. It's a good point too. Why are they mostly on the left?
Thanks again
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I have read of excess oil being pumped through the mainshaft, not sure how there is the pressure for it though.