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

[sgkent]

does the carb have only one outlet, and then the intake manifold bifurcates into two cylinders?

 

[slomo]

sgkent,

My ancestors were Colonial Scot and Native American.

Should be Colonial Scout isn't it? Simple typo?

 

[sgkent]

sgkent,

My ancestors were Colonial Scot and Native American.

Should be Colonial Scout isn't it? Simple typo?

Colonial Scottish, and Cherokee (probably Pamunkey), and also one of the Plains Tribes on my Grandmom's side although I did not learn about that until a year or so ago because her mom and dad divorced, and the Plains was on his family's side. Her father's family reached out to me a few years back when they realized their shared father had her in a prior marriage. The Scottish, and Native Americans didn't always get along that well during the 1600's and 1700's. So whom do I root for when they are fighting each other, my Scottish side or my Native American side? And there was some Scouting in there too during the War of Independence. My gg-grandmother was secretly raised by her grand uncle, Gen. Francis Marion, The Swamp Fox, when her father, (his nephew) was killed by the British during that war.

 

[slomo]

Colonial Scottish, and Cherokee (probably Pamunkey), and also one of the Plains Tribes on my Grandmom's side although I did not learn about that until a year or so ago because her mom and dad divorced, and the Plains was on his family's side. Her father's family reached out to me a few years back when they realized their shared father had her in a prior marriage. The Scottish, and Native Americans didn't always get along that well during the 1600's and 1700's. So whom do I root for when they are fighting each other, my Scottish side or my Native American side? And there was some Scouting in there too during the War of Independence. My gg-grandmother was secretly raised by her grand uncle, Gen. Francis Marion, The Swamp Fox, when her father, (his nephew) was killed by the British during that war.

So below your message body you have a blue section about your ancestors. That is what I was talking about.

My ancestors were Colonial Scot and Native American. I get really confused in old westerns whom to root for.

 

[gre1252]

When you swapped the coils over, did you try it with the kill wires removed ?
I ask this because you can get feedback ( which is what the diodes are supposed to prevent ) from one to the other
The fact that you got a faultering tach reading on one side & not the other points towards a bad magneto.

Also have a good look at the rockers
the cam grinds are identical , the followers are identical & the valves are identical
So if the cam is good both pairs of rockers should sit parallel at firing time & move the same amount.

If the head overheats then one of the guides ( usually the inlet ) can slip in the head so the inlet rocker will be out of place .

Yes, I removed both kill wires when the coils were swapped. The tach did act up on both sides with the kill wires removed. Putting the spark tester inline was the only thing that stop the needle from swinging at high rpms on either side.

I made markings on a plastic straw at or near tdc and bdc with the valves either open or closed. At the same piston position, on the opposite cylinder, the valves looked identical. Nothing felt out out of place from what I could feel with the straw on the piston and what I could see with the rocker arms and compression of the springs.

I thought it might be a sticky exhaust valve guide which is why I tried the blaster lmt in the cylinder first. I probably needed to spray the guide from inside the valve cover and exhaust port.

 

[gre1252]

So brother, this is puzzling. Again flywheel key just a micro tick off? You said it was checked already.

Could be excess fuel or air, SOMEHOW, getting into the muffkin, maybe dripping into it??

Carb needle and seat pressure tested to 7psi, holds for 30+ minutes?

Think your exhaust port needs pressure tested with 20-40'ish psi. These car evap system smokers are 1psi and under. Think they are 1psi MAX pressure.

I pulled the large nut off and the key looked perfectly straight. I bought keys just in case, but I didn't want to pull the flywheel if I did not have to.

I should have replaced the float needle but it was $16. I don't see any issues with it flooding or running rich on the spark plugs. The needle and seat looked new. I may have to pull the carb again so I will double check with a vacuum next time.

The paint can smoker I built has a low pressure propane regulator. It might be 1/2 psi. I guess I could plug the muffler pipe and bubble test for leaks. thanks

 

[gre1252]

does the carb have only one outlet, and then the intake manifold bifurcates into two cylinders?

Yes, the intake manifold bifurcates to two cylinders. There is only one outlet port.

 

[bertsmobile1]

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 .

 

[slomo]

I should have replaced the float needle but it was $16. I don't see any issues with it flooding or running rich on the spark plugs. The needle and seat looked new.

Pull the oil dipstick and smell for gas.

Still need to pressure test the needle for 30 minutes at 7psi.

 

[gre1252]

Pull the oil dipstick and smell for gas.

Still need to pressure test the needle for 30 minutes at 7psi.

I used gumout multi-tune in the oil and blaster lmt in cylinder 2. There could have been gas. I changed the oil 2 days ago and so far no gas smells or change in the oil level.

I'm not sure how to pressure test the needle with the air vents going to the float bowl. The test I've seen is to turn the carb upside down and pull a vacuum from the inlet port.