New engine backfires

MHasterok

MHasterok

New member
In a previous post I mentioned that I replaced my Honda engine (bent rod) with a 13hp from Harbor Freight. Guys at the local dealer got the regulator and everything switched to the new engine. It has been running great, but the last couple nights, it backfires at shutoff (whether I keep the trigger pulled or not). It is also hesitant to start once I go to restart it. I have to put the choke halfway or so (even if it is fully warmed up, and not cold outside), then it starts up again.

What would cause a new engine to backfire? It probably has about 15-20 hours on it.
 
Man your having a hell of time there...hope you get it figured out.
 
Backfiring at shut down occurs when gas is drawn in without spark while the engine slows to a stop. The unburned fuel hits the hot parts in the cylinder and it goes pop. Usually it's due to carbon build up glowing hot from the combustion, but I can't see a 20 hour old engine having a build up unless you're using really crappy gas.
 
Russ Johnson said:
Backfiring at shut down occurs when gas is drawn in without spark while the engine slows to a stop. The unburned fuel hits the hot parts in the cylinder and it goes pop. Usually it's due to carbon build up glowing hot from the combustion, but I can't see a 20 hour old engine having a build up unless you're using really crappy gas.
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That's what I thought. I usually get the gas at Shell, Circle K, or Chevron.
 
Russ Johnson said:
Backfiring at shut down occurs when gas is drawn in without spark while the engine slows to a stop. The unburned fuel hits the hot parts in the cylinder and it goes pop. Usually it's due to carbon build up glowing hot from the combustion, but I can't see a 20 hour old engine having a build up unless you're using really crappy gas.
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Or it is a China motor. You could look at the carburetor to see if it is seeping fuel, or you could shut off the fuel and let it run itself out of gas at shut down, if you have that option.
 
MHasterok said:
That's what I thought. I usually get the gas at Shell, Circle K, or Chevron.
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I'd rather push my truck than used Circle K gas......:nono:
 
Tony Shelton said:
Take it back to harbor freight and swap it for another one. A couple of wrenches and ten minutes out in the parking lot and you're on your way! :dance:
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Just drain the gas and your ready however it may take a few minutes longer to remove the charging system from the inneards of the motor
 
My briggs had a solenoid that shut off the fuel at the jet I think, to prevent 'afterfire'. Other engines don't have it - is it needed? Do you have the stock plug? maybe change that.
 
I have a 13from honda did the same thing. I thought it was the timing? It never ran smooth, but it always starts,
 
I have a 13hp honda that does the same thing. But that is the best motor ive come across in a long time. starts on the first pull, and it has bad gas in it still.
Anyone know if a backfire can harm the engine?
 
Chris Tharpe said:
Just drain the gas and your ready however it may take a few minutes longer to remove the charging system from the inneards of the motor
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That's the problem. The innards were installed from the Honda so it will charge the battery for the burner and starter. Too much hassle to take it back and swap it for another.

Tom, I'll try another plug. Any spark plug recommended?
 
I've always used the ngk's with that v cut in the electrode. I get the nippondenso's with the u-groove when I can find them.
 
tomtucson said:
I've always used the ngk's with that v cut in the electrode. I get the nippondenso's with the u-groove when I can find them.
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I'll look for those too, thanks.
 
My new 18 HP Vanguard backfires also but I'm not concerned since my riding mower has done it for the past 5 years with no long term ill effects that I can see........... However I might change the plug this year.
 
That is odd. My Vanguard 18HP has never back fired once and it has over 700 hours on it.

On the other hand my Kohler 15HP back fired from day 1...go figure.
 
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