is it possible?

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Sep 28, 2005
can engine oil get into the primary case? my primary was leaking the other day so I removed the level plug and a fair amount ran out. when I refreshed the primary last time with ATF-F I waited until no more ran out. this stuff is also pretty brown instead of ATF red, but then again I didn't clean the case out with kerosene or anything when I drained it last time. :?:
The crankshaft seal in the driveside crankcase is leaking into the primarycase. Its tucked out of the way behind the drive sprocket, with care you can replace it without splitting the cases by screwing in 2 or 3 self tapping screws and pulling it out.
mcsurf said:
can engine oil get into the primary case?

Allowing the engine to wet sump so that the level of oil in the crankcase reaches the crank seal doesn't help, also I believe oil can seep along the threads of the inner primary cover mounting bolts if they aren't coated with sealant when fitted?
the motor doesn't wet sump so it's not that. what's the downside of having some oil leak into the primary?
If it was a lot then you could possibly get some clutch drag and/or slip (when using large amounts of throttle).
And what could happen if you're using automatic transmission fluid in the primary and both oils get mixed in there?
I'm using 20/50 so I doubt I'm going to affect the clutch if I stay vigilant on the primary level. I just came back from a ride and it ran great but the primary level had gone up again. The bike has the anti sump valve mod done to the timing case so it doesn't wet sump much, and I ride it every day. Anybody else have this problem?
Check the crankcase breather setup. Pressure buildup in the cases can push engine oil past the seal into the primary. You may find other areas weeping oil because of this. Cylinder base gasket can also blow out from this problem :cry:
Don't be a stinge! Give the girl a new seal for her birthday....cure the reason for the wet sumping...(bet it is!) and donate the hour of worktime to her and cure her aches and pains. She will hug you for it.

The others are correct...there's too much oil in the sump and the seal is too old or, like said, pressure in the sump... Don't let it just be. Easy job, pull the front stator, chain and front gear, pull the seal out and replace, check that one of the three bolts hasn't unscrewed itself and isn't lying in the primary too, and make sure the sump pressure setup is free. Make her smile.... :wink:
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