# Massey35 backfire on shutoff



## westport109 (Jan 17, 2016)

Hi everyone
My MF35 gas runs pretty well. I replaced the thermostat this summer as I saw little if any coolant movement. During the process I had to replace the fuel bowl assembly as the valve would not shut off the fuel. The aftermarket unit drips, but the valve works and fuel is shut off when not running. My routine is to turn the valve on, do my thing, turn the valve off. I now get a major backfire about 3 seconds after ignition shutoff. Fuel still on. I also get a slight miss while driving. No smoke. Easy start. Wondering if I am not opening valve enough. I go about 1/2 turn. Too much? Too little? It is for doing snow on our road with a rear blade and does little work in the summer.
Any advice is greatly appreciated. 



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## HarveyW (Sep 15, 2014)

I'll give you a layman's explanation..... Your exhaust system has a carbon buildup that is very hot (maybe glowing) from exhaust heat. When you turn the key off, the engine continues to rotate for a few cycles as it coasts to a stop. During this process, unburned gas/air mix is pumped into the exhaust system. For some reason, it takes a second or two to ignite. I have a Honda engine on a pressure washer that does the same thing.


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## BigT (Sep 15, 2014)

Found the following statement on the internet: "Allowing the engine to idle from 30-60 seconds before turning the key to the OFF position will generally prevent this after fire condition."

Also, alcohol (ethanol) ignites at a lesser temperature than gasoline. If you can get gas without ethanol, it might help this after-fire condition.


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## John Liebermann (Sep 17, 2018)

BigT said:


> Found the following statement on the internet: "Allowing the engine to idle from 30-60 seconds before turning the key to the OFF position will generally prevent this after fire condition."
> 
> Also, alcohol (ethanol) ignites at a lesser temperature than gasoline. If you can get gas without ethanol, it might help this after-fire condition.


This should be a practice on all engine after working them. The cylinders need to cool down.


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