Briggs Coughing/Sputtering With No Load? Multiple Engines!

TylerFrankel1

TylerFrankel1

Well-Known Member
Hey everyone! I wanted to see if anyone else has experienced this issue before. It's minor but it's driving me nuts, because I can't figure out what's happening. I have a ton of small engines, mostly Briggs powered, and this season I noticed that several of my L-Head Briggs with the Float Style Carburetors (190CC usually) have been making a strange cough/backfire when running unloaded. It isn't loud enough to be backfire/afterfire, but it comes from the muffler and I have no idea what it is. You can physically feel it when holding the equipment. The carburetors are in good shape for each of the engines, I cleaned them to be sure, and the gas is new. The spark plugs should be fine. Timing is good on all of them. What gives? I recorded a few videos of different engines doing it. I just wondered if anybody else is experiencing this or knows why.



Gotta listen carefully, but it's especially noticeable on the second one
You also might notice the pressure washer has a slight rod knock. It was abused by its previous owner and I saved it just in time lol. I don't think that would affect this problem though.
 
I have a similar type mower with the Briggs that also does this. I've always assumed it was pre-ignition. Maybe from some carbon build up or a sharp edge or parting line in the casting. Mine is not near as bad (vid.2) but same type sound. Nice quiet powerful easy starting mower otherwise, I just run it.
 
Didn't think of that. I'll try scrubbing carbon out of them and put in higher octane gas to see if it changes. I wouldn't think the compression ratio would be high enough but it won't hurt to test. Maybe try some ethanol free too.
 
Sounds very much like you local fuel supplier has a bad batch of fuel.
Get some from a different branded place & see if it makes a difference .
Also check your fuel drum some times a little off fuel can make 5 gal go bad in no time flat .
 
bertsmobile1 said:
Sounds very much like you local fuel supplier has a bad batch of fuel.
Get some from a different branded place & see if it makes a difference .
Also check your fuel drum some times a little off fuel can make 5 gal go bad in no time flat .
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I'm gonna go nuts lol. I went to a different brand gas station today (I was using Shell, I went to a Quick Trip today). I got fresh 87 octane, 93 octane, and ethanol free 89 octane. I drained the carburetor and tank, cleaned the carb, and put in each fuel and ran the engine. After each run I would drain the bowl and tank and put in new fuel. I tested each fuel. STILL HAPPENS. Fuel isn't the problem.

So I figured carbon buildup may be the culprit. I took the head off and found normal buildup. I scraped off what I could (probably 75%) and no change. Maybe tomorrow I'll go get brand new spark plugs for all of them, but I don't think that's it. I'm gonna solve this though, if its the last thing I do.
 
Curious to know if you fixed it? I have a Craftsman YT3000 and it runs good, but has a sputter/miss as it runs. Still cuts the grass, but is such a pain not to run smooth
 
Coach Gates said:
Curious to know if you fixed it? I have a Craftsman YT3000 and it runs good, but has a sputter/miss as it runs. Still cuts the grass, but is such a pain not to run smooth
Click to expand...
Sadly, no, it's still happening. It bothers me too. I de-carboned the head of the motor, checked the timing and spark gap, cleaned the carburetor, etc. and nothing. Perhaps I should do a total rebuild, valve re-gapping, new gaskets, etc. to see what happens. Or try a different carburetor. I still want to know!
 
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