Oil in flywheel housing

[KiwiAde]

Somehow I managed to post this in "Wanted" Doh!

I removed the flywheel cover on my TY175 and found a puddle of what appears to be gearbox oil in the bottom of the housing. I have recently replaced the crank seals with new genuine seals. The bike is running fine - no excessive smoke and power is good. I am running ATF in the gearbox and 50:1 premix in the fuel tank.

Where could the oil come from? Only route I can think is from the clutch housing through the RH seal into the crank case then out the LH seal into the flywheel housing. If this was the case then surely she'd be running like a dog and smoking like a .... really smoky thing. Is there another route for oil into the flywheel housing?

Thanks,
Ade

[PA]

Somehow I managed to post this in "Wanted" Doh!

All fixed.

[David Lahey]

Here are a few unlikely ideas:
What if the other end of the flywheel case vent hose was connected to the gearbox vent fitting and the bike did a bit of gymnastics?
What if there is a hole in the rear of the flywheel cover and gearbox oil was leaking out the sprocket seal and being flung through the hole in the casing by the chain?
What if there is a leak into the flywheel case via the clutch arm position adjuster?
This is what is most likely:
What if it really is two stroke oil in there and the new LH crank seal is leaking? Leaks on that side don't cause exhaust smoke and only affect how well the motor runs near closed throttle.

One way to test would be to use different colour gearbox oil and see if the colour of the oil that appears in the flywheel casing matches.
Another test would be to take the stator plate off and have a real good look at the crank seal and see if there is a witness of the oil flow path.
Another test is to take the stator plate off and put soap bubbles all over the seal area and kick the bike over while watching for suck or blow.

[KiwiAde]

Thank you for the ideas. Now that you mention it, the gearbox oil was a pinky colour (since it was ATF) and the oil in the flywheel housing was brown. I'll remove stator and see if I can see where the seal is leaking.

[Tee-Why]

A leak down test would be good also, block off the inlet and exhaust ports, and inject a few PSI with a pushbike pump to a modified spark plug with schrader valve off an old inner tube and a gauge (or just measure with low pressure tyre gauge on schrader valve). Better with flywheel and stator plate off too if you go this far if you can see it leaking or not holding pressure over a couple of minutes. This will test the crank seals.

I made up some plates and used some rubber sheet to make a gasket, bronzed on a valve to an old plug.