Topic: 750K Oil Leak

[RebelSkyRot]

I've been chasing this oil leak for weeks now... It leaks out of the middle of the bottom of my transmission cover, but only after I've had the bike running. I've put two new gaskets on now, added some permatex to the one I put in tonight so we'll see how that holds up.. I know it's not leaking down the side of the generator cover as I've checked the rubber grommet and it's dry, but while I was installing my new gasket tonight I noticed this and am not convinced the hole is from the factory...


Any explanations for this hole? If there is indeed meant to be a hole there, any other ideas of where the leak would be coming from? If that hole isn't supposed to be there, I spose I'll try and patch it with a piece of Al and some good ole JB. Thanks as always guys.

[CB750F2]

I have just checked my spare motor and that squarish looking hole is there. I suggest that you remove the transmission cover and check the gasket and gasket surfaces for damage if you haven't done so already. Also, near the centre of the bottom edge of the transmission gasket surface, you will see a hole about 6mm in diameter. You would not see this hole if the gasket was in place. This hole should have a rubber plug and not be relying on the gasket alone to provide a seal. The plug is identified in the parts breakdown - the page with the two crankcase halves. Thanks, Pat

[scottly]

I don't see any hole that would cause a leak, or require J-B. The oil is most likely coming from somewhere else. The screw holes for the cover are "blind" holes, but if someone has put longer screws in, it can "pop" the inside end of the casting, allowing oil to leak past the threads.

[RebelSkyRot]

Scottly, it's interesting you say this because if my memory serves me right, the bolt where the oil is leaking right below is longer than the other bolts, maybe 5 threads or so. If this was the cause of the leak, how would I repair it? Drill it out to a 7mm or maybe heli coil to a 6mm?

[scottly]

Try wrapping some Teflon pipe tape around the screw threads, if you are sure that's where it's leaking. Three or four full wraps should do it.