Engine Sputtering/Backfiring

[rch316]

I have the following engine in my ride on mower https://www.engine-specs.net/briggs-and-stratton/40h777.html a 40H777 22HP V-twin and I can't get it running smooth. I have replaced the following with no success in fixing the problem. What am I missing?

1. carburetor
2. fuel pump
3. fuel filter
4. air filter
5. spark plugs
6. ignition coils
7. added new fuel

I confirmed vapor lock is not the problem by taking fuel cap off as the mower was stalling after running it for 30 mins before replacing all of the parts above.

I did find that when I run the mower and disconnect either one of the spark plug cables from the spark plug the sputtering stops. Does this mean anything?

Here is video of the mower running:

Any ideas? Thanks in advance.

 

[Craftsman Garage]

I would try adjusting the valves.

 

[rch316]

I would try adjusting the valves.

Thank you! That is a bit over my knowledge so I will have to send it to a repair shop for that.

 

[Craftsman Garage]

Or just look up a YouTube video-

 

[slomo]

camshaft time?

 

[Craftsman Garage]

Hmm, I would say that's unlikely. It doesn't sound like they've had the case opened up.

 

[Tiger Small Engine]

I have the following engine in my ride on mower https://www.engine-specs.net/briggs-and-stratton/40h777.html a 40H777 22HP V-twin and I can't get it running smooth. I have replaced the following with no success in fixing the problem. What am I missing?

1. carburetor
2. fuel pump
3. fuel filter
4. air filter
5. spark plugs
6. ignition coils
7. added new fuel

I confirmed vapor lock is not the problem by taking fuel cap off as the mower was stalling after running it for 30 mins before replacing all of the parts above.

I did find that when I run the mower and disconnect either one of the spark plug cables from the spark plug the sputtering stops. Does this mean anything?

Here is video of the mower running:

Any ideas? Thanks in advance.

I have a great idea. Clean the OEM (probably Nikki double barrel) carburetor that you hopefully didn’t not throw away. Install on mower and see how it runs. If you don’t know how to properly and thoroughly clean a carburetor, take it to a shop that can. These carburetors have to be dead on to run right.

 

[rch316]

I would try adjusting the valves.

I adjusted the valves, much easier than I anticipated. They were not far off from spec. Engine still spits and sputters.

 

[rch316]

I do not see anywhere to adjust the air to fuel ratio on this carb, is there supposed to be a place to do it?

 

[Craftsman Garage]

No, you cannot adjust the mixture on most carburetors due to emissions regulations. They are set from the factory. I suggest taking the old carb apart and thoroughly cleaning it.