Crankshaft gasket blown?

Smoke coming out of the sprocket cover, and/or the mag cover.

If you have a blown case gasket, there can be a leak on any one of the 4 seals. Some engines don't have a clutch shaft seals. Which case they can leak by the bearing.

Oil residue
 
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What's your bike doing DU? ...and what kind of engine you got before we guess any more. ;)
 
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on a ht a bad crank seal will sound fine with the clutch engaged but will have no power at all. if you take the side covers off look for oily exhaust carbon or smoke [joe] most of the time its only one side. dont flood the motor use the petcock it will happen everytime it floods. also check the center case gasket if no seal rupture.
 
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If a crankshaft 'seal' is bad, on the mag side, or pinion side, the motor will be difficult to start, and will not idle. The crankcase is part of the intake tract. same tests apply.


...if that is what you are referring to...

Good luck
rc
 
I had a crank seal go bad on the rotor side of an engine and the air leak it created caused the engine to rev as if it was on cruise control because of the lean condition the extra air was causing, it idled very fast and no amount of idle screw adjustment made any difference, that engine ran smoother than ever and made loads of power but was going to be toast very soon if I had not shut her down when I did.

This was my experience with a bad crank seal.

Map
 
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