Briggs and Stratton V-Twin Persistent Popping and Afterfire from Exhaust

[slomo]

 

[gre1252]

The engine symptoms have changed and now cylinder 2 pops when running on one cylinder. I went through a few tests and the dynamic compression is way off on cylinder 2 from what I had originally. I don't know if I damaged something running cleaners (gumout/pb lmt) in the oil and cylinder. The leakdown, static compression, and intake smoke test came back the same. It could be a bunch of issues from an intake cam lobe to a scored cylinder wall.

Running Compression Tests | ALLDATA

www.alldata.com

Does the intake manifold usually get cold enough to have condensate? I saw fluid in the bottom of both intake manifold ports on the cylinder heads. It was very clean and cylinder 2's port sits downhill on the manifold...

 

[slomo]

Does the intake manifold usually get cold enough to have condensate?

Not at my house with 107 temps LOL. Are you running alcohol fuel? Can you confirm water in the gas? Should be at worst just unsuspended fuel in the intake runner. This is a twin with a longer than most intake manifold.

Drain all the fuel out. Check for water in the pan.

I saw fluid in the bottom of both intake manifold ports on the cylinder heads. It was very clean and cylinder 2's port sits downhill on the manifold...

Sounds like your carb is passing mega fuel to me. Maybe one of the other real experts can chime in and assist.

Maybe remove the carb from the engine. Check for excess fuel leaving the carb at no crank and cranking.

 

[gre1252]

My desperation tool of last resort because I need all the hair I got left is a smart little device called a COLORTUNE made by Gunsens in the UK
Basically it is a spark plug with a window in it and by watching it you can see if the window flashes yellow , white or none at all when the engine stumbles.
You can also see the spark jump so no flash & no spark = magneto failure while no flash with a spark = fuel failure .
I set the camera to video mode with sound recording on a tripod to film the colortune so I can isolate the times when it misfires and then step through the video frame by frame in that period to see what is going on.
While it is very rare , you could try running the engine with the muffler removed just in case it is a back pressure problem causing the occasional choking
If you do this then try to leave the headder pipes on .
Not that you will be running the mower for that long you do run the risk of burning exhaust valves without a headder .

Interesting. I think it might be time to invest in a mini oscilloscope like the ds213.

I thought there might be a mouse (fluffy) in the muffler but it is not possible. thanks