Oil Leak after running

[smi481]

Has anyone experienced an oil leak from the rear of the engine
after riding the bike for a half hour or longer?

The bike runs fine, is oil drip free when cold, but after running
within a couple of hours .... a 3" spot of clear engine oil is
under the engine?

Screws are tight as well as the oil drain bolt with a new gasket.

After a day or two .... the oil drip dissapears and the bike
is dry as a bone? Perhaps some kind of drain line that
is routed behind the engine??

Any thoughts why it would leak after being run and while
being at running temperature - with the oil leak stopping
after the bike cools off?

Thanks for any help you can give.

sm481

[Waveblaster]

assuming the gaskets and seals are ok it could be blow by from the head. It could be oil dripping after condensing in the breather behind the engine.

Perhaps you could lay an old large mirror underneath while running and something may become apparent.

[pojobey]

I have noticed a similar leak on my CB77. It appears to be coming from one of the two rectangular drain/vent holes on the right underside very close to the right exhaust pipe. It does quit after a day or so but it ain't getting any better either! Did you figure yours out yet?

Thanks,
-pb

[Bob Dale]

I've got the exact same problem with my '66 CA77. After a short ride it drips several tablespoons of oil from the bottom of the right side engine cover. It's hard to tell exactly where its coming from because it spreads all over the bottom of the engine. Makes a real mess wherever I park it. After about a day it completely stops, even when stored vertically on the stand. That seems to indicate that maybe its not the bottom of the main crankcase cover gasket but possibly some internal seal that is normally above oil level and only sees oil while the bike is running. Possibly the sprocket shaft seal? I have clear breather tubes and there's no oil showing up there so I don't think it's blow-by. I was going to pull the right side engine cover to check the gaskets and seals behind it when I found this post. Anybody had and solved this problem before?

[Hamamatsu Nippon]

A common oil leak for our engines occurs from the right side cover. There is a small drain cut out in the bottom of the engine cover. There is no gasket on this cover since no oil should be found in here. Inside the cover are two walls that contains lost engine oil and sends it out the drain. Honda rightly so, cut that drain just below the crankshaft oil seal, and the starter sprocket oil seal just in case of seal failure. It is likely the starter seal that is leaking but could be the crank seal. You have to pull the stator to get at the seals.
My engine leaks from this drain as well. I'm going to fix this in the winter when I find the correct seals.

[Bob Dale]

It's been a long time since I've had that right side cover off. I forgot that there's no gasket there. Your starter or crank seal idea sounds right. I guess we're on the same quest for those seals. I will update the post if I find them. Thanks.

A common oil leak for our engines occurs from the right side cover. There is a small drain cut out in the bottom of the engine cover. There is no gasket on this cover since no oil should be found in here. Inside the cover are two walls that contains lost engine oil and sends it out the drain. Honda rightly so, cut that drain just below the crankshaft oil seal, and the starter sprocket oil seal just in case of seal failure. It is likely the starter seal that is leaking but could be the crank seal. You have to pull the stator to get at the seals.
My engine leaks from this drain as well. I'm going to fix this in the winter when I find the correct seals.

[Steverino]

My 1975 750 has that same leak but I'm waiting until I finish a couple other motorcycles before I start taking it apart. Thanks for the info!
Steve