Smoking on startup after sitting awhile

[Guest]

Its been about 5 weeks or so since i got out on the 750 so i'm planning for an extended scoot on the upcoming long weekend. Tonight I went out to the man room to start her up. Wouldn't start without full choke for a second or two but as soon as it fired it started to belch black smoke out of the right side. It had never done that before. It did it for a good five minutes and it really was belching out. Twisting the grip made it smoke like a destroyer putting out a smoke screen.

After shutting it off and restarting it a few times it started normally and wasn't shooting out any smoke. I let it idle again for two or three minutes and revved it a few times but no more smoke.

I'm kind of at a loss to understand this as I've never experienced that before on this or any other bike. I think the carbs are set a bit rich but

I have a bit of Seafoam in the gas but I don't think that would do it. I'm stumped. I don't think anything is wrong and the engine sounds normal so I'll stick to the plan and get out for a scoot.

Anybody have an idea what's going on?

Cheers all.
Spyug

[Nessism]

If the smoking was from the left side I'd suggest that maybe your petcock is leaking and the cylinder is filling up. Maybe one of the floats on the right side is leaking?

[speedzter2000]

Maybe the gas? I thought I read somewhere after two weeks of sitting the chemistry in the gas changes. Did you treat the gas before putting it away? Sounds like carbon if it's black.

[spyug]

Thanks for the interest and input. The Seafoam is a fuel stabilizer I'm told so I don't think the gas had gone bad. I'm not all that sure that the #3 &4 carbs aren't set up a bit rich. I was in a bit of a hurry to get the bike on the road when i first got it so the carb clean and rebuild was just a quicky. My intention was to do a thorough job over the winter.

When I first got it on the road it wouldn't idle properly but ran very strongly. After a week or so it began to idle at rest no problem and still ran very strongly so i thought it was mostly sorted. I did notice the smell of gas a few times so I thought it was likely running too rich overall. Tis belching smoke was something new.

I'll give it a good run this weekend and see what happens.

Cheers all,
Spyug.

[t3rmin]

Valve guide seals? Oil leaks past when sitting, then burns off when you start it. You wouldn't see much/any smoke while running, only starting after it sits. My Tercel does the same thing.

Does it do it every time you start it after it's been sitting for a while?

[Nessism]

Valve guide seals? Oil leaks past when sitting, then burns off when you start it. You wouldn't see much/any smoke while running, only starting after it sits. My Tercel does the same thing.

Does it do it every time you start it after it's been sitting for a while?

Too much gas leads to black smoke, oil burning is white/blue smoke.

My guess is a sticking float causing the carb to overfill and run rich. Make sure the petcock is working properly: only flows when on Prime or when a vacuum is present.

Good luck.