# Black smoke on acceleration. Reason and remedy?



## orangputeh (Nov 24, 2016)

I have a Honda HS928 that starts and runs well. But when i go thru idle to fast a puff of black smoke comes out but it still runs ok.

there is a smell of gas and i know that black smoke indicates unburnt gas. I was wondering what i could do about this and should it be a concern.

like i said, it starts well. it runs good. is it slightly flooding? or do i need to change something in the carb? this carb has the locked out air-fuel mixture screw .

will this eventually cause problems down the road?


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## jsup (Nov 19, 2017)

Do a leak down test. And as the old joke goes..."it hurts when I do this".....don't do "this". 

A leak down test will tell you what you need to know. It could be oil, not gas.


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## Kiss4aFrog (Nov 3, 2013)

All that comes to mind is maybe the float is set a little high or it's hanging up a bit where the engine can suck too much gas too quickly.
Moving the throttle slower from idle to fast should help. I'd also run some fuel system cleaner through it if you haven't already. Might save you from having to pull the carb apart in the near future if it is a float or needle/seat problem.

.


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## nwcove (Mar 2, 2015)

I wouldnt worry about it. My 208 cc chonda does the same thing if i open the throttle quickly.


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## stromr (Jul 20, 2016)

Could be worn rings or valve seals. Here's a little light reading you might enjoy. Could also be the momentary rich condition a carburetor produces under sudden acceleration from increased airflow thru the venturi over the main jet and nozzle.

My Engine Is Blowing Smoke! What Does It Mean? ? Auto Advantage


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## Prime (Jan 11, 2014)

I dont think its a concern. Almost every small engine that I have ever owned would give a puff if move from idle to full throttle quickly. Engine needs to catch up to the rate the throttle is being applied. Doesnt sound to me that you have an issue.


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## jsup (Nov 19, 2017)

stromr said:


> Could be worn rings or valve seals. Here's a little light reading you might enjoy. Could also be the momentary rich condition a carburetor produces under sudden acceleration from increased airflow thru the venturi over the main jet and nozzle.
> 
> My Engine Is Blowing Smoke! What Does It Mean? ? Auto Advantage


Why I suggested a leak down test.


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