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CB750F Breathing heavy??

Yes that is very excessive smoking, there should be none or very little. Could be condensation burning off if the oil has been in it a while. Have seen fuel diluted oil do that as well. Or in worst case could be very excessive blowby. Either worn rings or stuck rings if it has set for a long time.
 
Yes that is very excessive smoking, there should be none or very little. Could be condensation burning off if the oil has been in it a while. Have seen fuel diluted oil do that as well. Or in worst case could be very excessive blowby. Either worn rings or stuck rings if it has set for a long time.
Thanks for the response. The bike had been sitting there for a few months at most. I recently changed the oil and filter, spark plugs, coils, new wiring harness, and new regulator / rectifier combo, changed the oil hoses and I sprayed the engine. I also took it to a mechanic and had the carburetor synchronized.

I took it for a good ride for around an hour and the bike seemed to run ok bar a few flat spots here and there and of course the smoke once it got nice and hot. I got back home and still smoking the same. The breather was a little wet and smelt more like fuel / water to me. See the video below.

How do I find out if it's a stuck ring?? Compression test??

https://youtu.be/wRkMVHCvywo


 
Compression test is a good place to start. If the smoke smells like fuel then it sounds like you have a lot of fuel dilution in the oil. Guess I would ride it a couple times on some longer runs to get it up to operating temperature see if it gets better. It could be too rich and loading the oil with fuel. It really doesnt sound like it is running very smooth in the video. Where do you have that vent coming from? Is it run from the valve cover?
 
Compression test is a good place to start. If the smoke smells like fuel then it sounds like you have a lot of fuel dilution in the oil. Guess I would ride it a couple times on some longer runs to get it up to operating temperature see if it gets better. It could be too rich and loading the oil with fuel. It really doesnt sound like it is running very smooth in the video. Where do you have that vent coming from? Is it run from the valve cover?
I adjusted the air screws on each carb to run a little leaner.

Yah from the valve cover.

 
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