• Enter the March CB750 Supply gift certificate giveaway! It's easy... Click here, post something, and you're entered into the drawing!

CB750K DOHC oil "sweat"

Motorhead

CB750 Enthusiast
Messages
53
Reaction score
0
Points
6
Location
Israel
My bike developed oil leaks and oil "sweat spots" in all sorts of places (mostly drive sprocket seal, vertical camchain tentioner rear bolts, oil pressure switch etc.), all as if there was excessive crankcase pressure.
There was also such a "sweat spot" where the right vent tube connects to the case.
That led me to think that crankcase vent lines were blocked, but they are not. There's also very little oil in the airbox and in the airbox draining hose. (I remember there wss usually more).
The airbox is stock, air filter is a paper one.
What else should I be looking for?

Thanks!


 
I generally do away with the OEM breathing setup, using a simple setup that takes the OEM tee at the two main pipes to run high to allow most oil to drip back into motor, then it drops back down to enter the collection notch at back of motor on the right side, where all the carb lines went in OEM condition. Make the downdrop long enough to actually hang below the engine looking underneath it to wave in the wind by at least one inch and you have a vacuum sweep at driving speeds that keeps very light suction on it to flow better.

Your other issues are loose hoses or worn seals, a bit of oil misting over long periods is normal, a lot quickly is not.

Engine in less than ideal condition will pump more oil out due to blowby increasing past the rings, you may have a problem developing there.
 
I generally do away with the OEM breathing setup, using a simple setup that takes the OEM tee at the two main pipes to run high to allow most oil to drip back into motor, then it drops back down to enter the collection notch at back of motor on the right side, where all the carb lines went in OEM condition. Make the downdrop long enough to actually hang below the engine looking underneath it to wave in the wind by at least one inch and you have a vacuum sweep at driving speeds that keeps very light suction on it to flow better.

Your other issues are loose hoses or worn seals, a bit of oil misting over long periods is normal, a lot quickly is not.

Engine in less than ideal condition will pump more oil out due to blowby increasing past the rings, you may have a problem developing there.
Thanks for stepping in. Ring wear would first result in engine burning oil, wouldn't it? There's absolutely no smoke from the exhaust whatsoever.

 
'Ring wear would first result in engine burning oil, wouldn't it?'

Blowby increases before you get to that point. You have even a certain amount of it in a well running engine. A strong ignition system will burn a certain amount of oil before the oil smoke shows also. Check your tailpipe exit, if the carbon is solid dense black rather than somewhat very dark gray, you may be there.
 
Back
Top