Exhaust smoke when engines off????

R

Riffter

Guest
Sorry 'bout this folks - got a prob with my Jap Bike (guilt and shame..) and I'm stumped.

Problem is that sometimes when I turn off the engine, small wisps of smoke will come from the exhaust? Doesn't matter if I've been on a long haul or just down the shops, it can still happen - it's as if something in the engine is still combusting?

I'm supposed to be selling the bike to fund my Sporty - I dropped on an ace Sporty and bought before I've sold. But I've got too clear a conscience to sell something that's not right.

I'd be real grateful if anyone's got any ideas, as I need to fix this so's I can pay off my credit card and appease the Missus!! :(

Riffter
 
Re: Exhaust smoke when engines off????

does it smoke when it runs? what colour is the smoke?
 
Re: Exhaust smoke when engines off????

Seems standard when it runs, really. Perhaps a bit more smoke than usual, but it's been below freezing here, and on an automatic choke.

Colour is also normal - not blue or black. BUT when the engine is shut off after running the wisps of smoke are a grey/black colour.

I was thinking of giving it an oil change - I did one about 1,000 miles ago, but I do hammer it a bit. Could this smoking business be caused by old oil??

Cheers,

Riffter
 
Re: Exhaust smoke when engines off????

Nah, I dont believe so. Oil **escaping** gives you smoke, not oil that's a bit old. And at 1,000 miles your oil will be sound.

In general ...blueish (oil) smoke on deacceleration is typical for worn guides/seals. Blueish smoke all the time and when under load is typical for worn rings.

But yours is black smoke? Usually fuel. It just might be running a bit rich ........ and there's a bit much fuel sitting round at the close of play. Automatic choke not tip-top? Or staying on longer in extreme cold and you are seeing the results of a few SHORT runs.
 
Re: Exhaust smoke when engines off????

Is it DEFINITELY smoke, or is it steam? Don't forget that burning hydrocarbon fuels produces water, which can collect in the exhaust (this is why they rot from the inside out) and may trickle out as vapour once the bike is stood and switched off.
 
Re: Exhaust smoke when engines off????

Hmmm? Strange business. The bike is only 9 months old from new. So unless there's some sort of anomoly, I'm thinking the seals will be OK.

Don't think it's steam either, as it smells very pungent, although I s'pose steam could do??

Possibly the 'Short runs' idea though Dave! I only work a couple of miles away, but I always go on my bike, as the missus has the car to run the kids about.

I usually go for a spin in the sticks before and after work - give it at least 15 - 20 mile run. However, since the weather got really savage (late December-ish) I've buggered it and headed straight to work and straight to home. Believe me, something I definitely won't do on my Sporty!

The smoke does decrease when the weather's been better, but the weather hasn't really got that much better yet.

Do you think there is a possibility of long term effects of such short runs and lengthy use of choke, or d'you reckon this will dissipate come 'sunny' Spring??

Thanks Again,

Riffter
 
Re: Exhaust smoke when engines off????

The smoke does decrease when the weather's been better, but the weather hasn't really got that much better yet.
Click to expand...

I'll go with kev on this one, and you just confirmed it in my mind, its water vapour.
yes it will smell because its sitting in your silencer where all those nasty hydrocarbons acids and soot gather.
its there because internally your exhaust hasnt completely warmed up to operating temperature, and what is happening due to the cold weather the pipe is chilled causing the water vapour to recondense in the pipe, then when you stop it falls back to the hot section of the pipe boils off and emits like smoke when you have stopped the engine, and it doesnt do this when running because of the constant flow of gases as exhaust.
long term I would expect it to rot you pipes (thats why car exhausts rot so easily)
get rid now and get that sporty you are hankering over:)
 
Re: Exhaust smoke when engines off????

Cheers, all!

Thanks for putting the latter into words, S.T. - that sounds about right. I wanted to make sure there were no major engine issues, 'cos I wouldn't wanna sell it to someone if it was dodgy.

I'm kinda over the moon 'cos I've already got my Sporty, S.T.! :) It's bloody lovely, and beautiful to ride compared to anything I've had before.

But now I've gotta settle up the finances! :eek: (Plus customise the beast to kingdom come :rolleyes: !!)

Riffter
 
Re: Exhaust smoke when engines off????

Hi
I thought it could be the exhaust valves on one of the cylinders being open when he turns of the engine and unburnt mixture escapes. but then again if the exhaust is open it should not be unburnt. But I would not worry as it used to happen to my gsx, and my mates fazer :eek: and the bikes were fine.
quite normal I'm told.
 
Last edited:
Re: Exhaust smoke when engines off????

As above, I have had this happen to both Hondas, 1000F, Blackbird, it does not happen if you just switch off the motor:D that last blip (I figured) turns off the sparks before the revs, thus, unburnt mixture flows into the exhaust and exits the rear as light grey smoke, can look cool:cool: .

Speculation only but sounds about right:D
 
You must log in or register to reply here.
Back
Top