Ruff Running Briggs & Stratton Twin

[Johnypat]

My B & S model 406777, Type 0117 EI, Code 97111?YG runs as if the choke were partially out even though it isn't. The spark plugs look good and there is spark being generated. It starts fine, idles roughly, will run at high speed.
While running it without the air filter at low speed it occasionally backfires thru the carb.
I can't find any carb adjusting screws; are there any? I have replaced all filters.
Can anybody help me make it run smooth again?

Thank you

Johnypat

 

[oldnslo]

My B & S model 406777, Type 0117 EI, Code 97111?YG runs as if the choke were partially out even though it isn't. The spark plugs look good and there is spark being generated. It starts fine, idles roughly, will run at high speed.
While running it without the air filter at low speed it occasionally backfires thru the carb.
I can't find any carb adjusting screws; are there any? I have replaced all filters.
Can anybody help me make it run smooth again?

Thank you

Johnypat

Johny,
Have you tried replacing the float inlet needle and seat assembly. These wear over time and can allow extra fuel to be pumped through the carb flooding the engine, this is especially true with engines that have fuel pumps such as yours.

I do not believe there are any adjusting screws on this model.

Roy

 

[hawkeye08]

If you haven't run it for awhile or the gas is getting a bit old, it may just need some cleaner through it. Seafoam works well and there are others.

I bought a used Honda generator that had been stored for 12-15 months. The seller had changed the oil, drained and refilled with gas tank with fresh gas and when we listened to it run before we bought it, it was running a bit rough and surged some. I bought it, brought it home, put some Seafoam in the gas tank, an ounce of Lucas fuel treatment and ran it under varying loads until it used the whole tank of gas, then refilled with fresh and it runs very smooth, no surging or roughness at all.

If it has been running fine and just starting running rough, then I would suspect some debris got into the fuel line and is causing problems. You might need to clean out the fuel bowl and change the fuel filter.

good luck..

 

[yooper1]

I would replace the plugs even if they appear to be good.

I have come across the popping at least 3 times on B&S engines and it cleared up with new plugs.. (probably B&S branded champions in it.....I never cared much for champions)

trust me...(I deal with versions of this engine from November 1st to April 15th every year)

it is the cheapest thing to test

No guarantee, but I would

 

[Treemonkey1000]

If it has the big float bowl type of carb drop off the float bowl and look for crud on the bottom. If if uses the same type of carb as Tecumseh the carbs can fall apart sometimes. I had to replace the carb after going through the same thing you have going. Another thing to look for is if the gasket between the carb and cylinder heads is leaking. Spray some carb or choke cleaner around the intake port while it is running to see if that affects how it is running.
Another thing to look for if the springs and governor vane are gummed up.

 

[mostly_gas]

If carb work doesn't help, then pull flywheel and check flywheel key for damage.The fly can shift and that changes the timing on the engine.

 

[puckgrinder85]

I would try plugs as well, cheap and sometimes does work (just did this on our husqvarna lawn tractor). Backfiring through the intake sounds like its lean however.