burning gear oil?

[knobbyboy]

A friend's 250R will run great for about 30 min. Then it begins to smoke- a lot, smelly smoke, then it will foul the plug after a while. A fresh plug will get it running again.

We're guessing that the clutch side crank seal is giving out and its sucking in gear oil and burning it. Mainly because of the excess smoke and the smell.

Anyone had this problem? How was the fix? Other ideas or possibilities?

[C-LEIGH RACING]

Only 2 ways transmission oil can get to the crank, through the center case gasket if it should be leaking or from the clutch side crank seal.

To test the crank seal, drain the transmission oil, put the bolt back in & then pour a whole qt of dexron ATF in the trans, crank it up & ride. Should smoke right off even before it gets hot if its the seal.
One good thing about it smoking, that oil being sucked it keeping the engine from locking up from an air leak.
Neil

[knobbyboy]

So if the seal is bad does that mean that the crank bearings are going away also?

[Rich250RRacer]

Originally posted by knobbyboy
So if the seal is bad does that mean that the crank bearings are going away also?

No, a seal could be bad and the bearings can be fine. I make sure I change the collar that the seal rides on EVERY time I replace a right side seal. The old seal will wear grooves in the collar and the new seal will not seat properly.