B&S Won't stay running (new carb) - runs if I restrict carb airflow

[nullRequest]

I've got a B&S (125K02-0187-E1) that won't stay running. I've done a bunch of research and the obvious culprit is the carb, but I just replaced the entire carb with a brand new OEM one, and it didn't help. It was a replacement motor I got on Craigslist to replace the one on my Super Recycler that crapped out. It feels like it's got good compression comparing to other mowers I've had in the past.

The weird thing is that if I start it (with a small squirt of thrust), then restrict the air intake on the carb, I can get it to keep running (basically a redneck choke). Here's two videos showing what's happening.

This one shows it will start, but die almost immediately: https://vid.me/9C19

This one shows me keeping it running by covering the air intake with my hand: https://vid.me/PMbH

Brand new carb, spark is good and right gap, fresh full tank of gas. After new carb didn't help, I just replaced the oil, which was pretty dirty, so I put some seafoam in the crank case to run a bit. Before I put on the new carb, I could get it to keep running if I kept pushing the primer and feeding it more gas, which is why I figured maybe the carb was clogged/shot so I took a chance on a $30 new carb, which didn't help.

Thoughts?

 

[lugnut1]

from the video it has a definite fuel supply problem
(sounds like it may have a little valve slapping going on)
oil at proper level?

possible causes:
1. low compression (not enough draw)
2.intake manifold tube (something in tube restricting air flow) or (tube loose or damaged), also possible gasket leak)
3. carb has fuel restriction (needle-float not working properly)
4. tank fuel line restricted

(some of these type of engines have a fuel shut valve next to air filter box not sure which models.)

 

[lugnut1]

watched your second video again
looks to me more like a low draw problem

1.exhaust valve has seating issue (seepage) it will allow engine to draw air through it on intake stroke causing low draw
2. intake valve not opening far enough causing low draw.

just some food for thought

 

[Tinkerer200]

Might try shooting carb cleaner or WD40 around gasket areas, if change in running, gasket leaking.

Walt Conner

 

[nullRequest]

I ended up getting it working. Here's what I did:

1) Added seafoam to the engine oil.
2) Started it, and kept it running by restricting the airflow into the carb. I kept the redneck choke on and let it idle for about 3-5 minutes. My goal was to mix in the seafoam and slosh it around to all the internals as oil was moved around during operation.
3) Changed the oil, which was quite murky. (Not sure when it was changed before I bought it). Replaced with fresh oil & added additional dose of seafoam to the new oil.
4) Later that evening, started and redneck choked to idle it for 5-10 minutes but it still wasn't working that great (only started with starter fluid & wouldn't run unless airflow was severely restricted)
5) Next morning, it almost started once w/out starter fluid. Started with a tiny spray of starter fluid and kept full redneck choke to keep idling for 5-10 minutes As I was going, it seemed to gradually need less choke and eventually I was able to stop choking it completely. Starting no longer needed starting fluid, only needed to use built-in primer and a number of good pulls on the starter to get to start.
6) That evening, I was able to start with just the built-in primer bulb and mow the lawn. (engine time of about 1.25 hour).
7) Changed the oil again for good measure after mowing the lawn w/seafoam and it was fairly dirty again.

As of now, it starts & runs well, with just a priming and a standard pull to get it to start.

I've got one of those tiny inspection cameras, so prior to all this, I pulled the spark plug and didn't see any scoring of the cylinder walls. The valves were a bit carbon covered, but seemed to seal ok (and I had OK compression).

This is a very weird situation, so I'm posting my results in the hopes that it helps someone else from going through all the struggles I went through!