I have a 1973 CB750k3 that I just rebuilt from the frame up. However, I am noticing a black sooty smoke comming from #1 and #2 exhaust. No visable problem with #3 and #4. I have changed plugs and re-timed the engine (new point set) to no avail. I have not fooled with valve clearances as yet and am wondering where to go next. Engine does seem to 'bog' down slightly at lower speeds and then kicks in. Any suggestions to get my bike running like it should would be greatly appreciated. Thanks for any help ..... Mike D.
