Outdoor Power Equipment and Small Engines - Rough idle, almost stalling under load

I've got a 3 year old MTD with a 4 HP B&S. While mowing last week, the engine started to act like it was out of gas. I checked the tank, no problem. Then cleaned the air filter, still didn't solve the problem. Replaced the gas with fresh, still not solved. If I watch the carb with the air cleaner off, I can see the choke open and close as the engine revs and then almost stalls. The manual says the carb is not adjustable and I don't see any adjusting screws. There is no idle speed adj linkage either. The engine starts fine after priming and runs well for about 3-4 seconds, then starts misbehaving. I continue to suspect fuel problems. Is there anything else I can try or should I take it in to the shop?

Hello Shearwater!

That engine shouldn't have a choke. Sounds like you might be seeing the throttle open and close. I believe you need to replace the carburetor diaphragm. Very easy job.

What are the engine ID #'s? We can then advise further on procedure and parts needed.

B & S Model 10A902/Type 2189B3

I'm looking at the pdf on the B & S site, looks like maybe a 495770 - carb diaphragm?

I also see a diaphragm kit listed, part 5083. Says it fits most 2 - 5 HP engines.