What does it mean when...

[Jethro]

... I have dark smoke coming out of the exhaust on start-up? When it gets warm, there is no smoke. Am I burning oil?

[KEITH KRAUSE]

If it's dark (black/dark gray) it's unburned fuel.
If it's white/whitish blue, it's oil. Typically, oil leaks at first appear only at cold start ups. The engine clearances are wider when the motor's cold. As it warms up, the clearances tighten up and the oil can't get past the rings, valves, etc, that's causing the leak. With more time/miles, the oil leak will start burning all the time.

[Jethro]

As usual, thanks again Kieth! From your description, it seems like dk grey smoke. Should I worry about it?

As a continuation from my other post you have been helpful on, the bike seems to start much easier now. But does the smoke mean I am probably running rich when cold (unburnt fuel)?

[redliner1973]

does it have a strong fuel smell to the smoke?

[KEITH KRAUSE]

If it's dark gray, it's unburned fuel and it should smell pretty strong.
Dark exhaust from a rich mixture will not linger like burning oil. You should be able to smell/see the difference. A rich mixture should stay with the bike, even after it's warmed up. As the bike warms up, the motor actually runs richer in normal operation. Oil burning, at first, usually shows during cold start ups only and later on shows at all engine temp's.
A dark exhaust is either a very rich mixture or a weak spark. This will cause poor performance, poor gas mileage, dark or fouled plugs and excess carbon deposits.
How bad it is depends on how much is coming out the exhaust. Just a little smoke while revving it could just be a matter of lowering a jet needle or a smaller jet. Can you see it while idling, or do you have to rev' it? You're sure it goes away when hot?
Why is the bike starting easier? What exactly did you do? Did the dark exhaust just now start happening?

[Jethro]

I can see and smell it at start up, idle or higher. In about 45-60 seconds the smoke goes away- not really sure about the smell, I'll have to pay more attention next time. Yes, it did start happening recently. All I did was change the fuel line to the proper 5/16", clean the carbs fully replacing two float jet o-rings that were badly worn, reset the float heights that were badly off and re-synched the carbs.

[KEITH KRAUSE]

Well, if it started right after the carb work, I have to think you did something wrong.
Cleaning the carbs and then getting a rich mixture like that would probably mean you adjusted the float height(s) too rich or you didn't get the carb synch levels close enough to each other. Unless you left a jet loose or something.
It only takes one carb to cause the problem. Any fuel coming out of one or more of the float bowl overflow lines?

[shortlid]

Rich mixture

If it's dark gray, it's unburned fuel and it should smell pretty strong.
Dark exhaust from a rich mixture will not linger like burning oil. You should be able to smell/see the difference. A rich mixture should stay with the bike, even after it's warmed up. As the bike warms up, the motor actually runs richer in normal operation. Oil burning, at first, usually shows during cold start ups only and later on shows at all engine temp's.
A dark exhaust is either a very rich mixture or a weak spark. This will cause poor performance, poor gas mileage, dark or fouled plugs and excess carbon deposits.
How bad it is depends on how much is coming out the exhaust. Just a little smoke while revving it could just be a matter of lowering a jet needle or a smaller jet. Can you see it while idling, or do you have to rev' it? You're sure it goes away when hot?
Why is the bike starting easier? What exactly did you do? Did the dark exhaust just now start happening?

Ok, I am geting the 1-2 seconds of gray smoke on start-up and the poor mpg. Also all of our5 cloths smell like gas after a ride. But my '80 GS850G is stock jeted (which I hear is LEAN). But I do have 1100G pipes (bigger) and a K&N air cleaner in the stock air box?? The question is am I running rich?

[shortlid]

Leaking petcock could be issue??

Leaking vac. petcock?? A memeber stated that a leaking vacume petcock could be my issue how could this be?? Can the the gas get past the diaphram and get into the intake? The petcock was rebuilt with new seals a year ago??