Is this the infamous oil leak? 77 GS750

[Nessism]

Black smoke is too much fuel.

Please check the Newbie Mistakes thread linked in my signature. It may help you know what needs to be done.

[Mickeymoe]

I agree with Nessism, that black smoke indicates too much fuel. However, black smoke can also be caused by a weak spark (low high voltage, possilbly a bad coil) or by badly fould spark plugs. What I would do if I had your issue is first replace the spark plugs, and then adjust the fuel mixture screws and try and lean out the bike. Not sure if you replaced some engine gaskets, but a scenario might be that the engine was mixing air being sucked in through gasket leaks and now that those leaks are plugged there is not enough air to mix with the fuel. Also check to see if there are any restrictions in your air box or air filter. You could try starting the bike with the filter removed and see if there is a noticable difference.

Mark

[Jordan]

Black smoke is too much fuel.

Please check the Newbie Mistakes thread linked in my signature. It may help you know what needs to be done.

thanks... Dit it long ago when I registered. Main thing is the leak...