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Like you said. Oil from the primary is gonna get sucked up by vscum pressure and not the other way stound. Makes sense!
as far as overfill, I can’t imagine how that is even possible. 3/4 of a quart? That a lot of oil
Yes it is!
With that short primary it'd have to had been full to the top of the clutch cover for that excess amount. For the sake of the OP I'm hoping he simply opened the cover on the side stand and spilled some without a drain pan in place. Just a 1/4 cup of oil or fluid spilled will make a BIG mess on the floor. Or maybe someone serviced it by draining then refilling thru the pipe plug on top of the inner primary and dumped in 2 rather than 1.5 quarts.
Now that you mention it - if the bearing spigot is so loose that it could have that much in the primary, it'd have to eventually pull some back into the crankcase and stabilize the oil tank level at some point. All this is assuming he just bought this thing and the previous owner knew about this and ran it till the levels evened out and sold it. Let's send good vibes to the OP and hope it's all just a boo-boo on the service end
If the crank seal is leaking, it will only pull fluid out of the primary into the engine. I'll spare y'all the long story as to how I know that, but will say - it's a long ride from Seattle to Charlotte using a turkey baster and 7/16" wrench at every fuel stop...
There's only 2 ways for that to happen. A missing "screw" from the rotor connector clamp (red circle) or most often, the bearing sleeve is loose in the engine case usually causing a crack that's sometimes near impossible to see. (yellow arrow). Again, and even if it's totally shot, the seal will NOT let enough engine oil into the primary that you could ever measure.
Verify you're actually "making" primary fluid is the first thing to do before you panic. And yes, you won't notice much, if any engine oil missing until the primary is way overfull, if it's the bike fault. Let's hope your overfull issue was just a fluke mistake from the last engine service.
I always thought engine pressure would push oil into the primary pass a bad crank case seal and or stator screw holes. Never knew it could suck oil back to engine?
I always thought engine pressure would push oil into the primary pass a bad crank case seal and or stator screw holes. Never knew it could suck oil back to engine?
One would think so but the breather gear is timed so there is a negative pressure on the flywheel side of the engine on upstroke. That's why the seal installs "lip out" on a wet primary to keep the primary fluid from being sucked to the crankcase. I've seen several suck the primary nearly dry from a bad seal and one from a seal in backward. Had it happen to me once due to a bearing spacer (that the seal runs on) that I'd over dressed. It was only .020 smaller than a new one and even with a new seal, after 125 miles of highway speeds it would pull the primary near dry and the oil tank be so full it couldn't vent. That makes a strange sound when the oil tank can't vent
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