Oil on that side of the time wouldnít come from the exhaust, more like the clutch breather, cover or rear hub seal.
Clean the motor real good, dust it with baby powder and take it for a ride.
If you still suspect your clutch side seal, youíll be blowing billowing white smoke and starting will be more difficult up to the point the seal is toast. You can also check your gear oil for gasoline mixing with it.
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