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Discussion Starter · #1 ·
I have about given up on my old B&S 12 hp vertical shaft on my Snapper RER. It started suring and stalling really bad this spring.

Here are the symptoms: it starts and runs good cold, but after about 10 minutes under load it starts bucking and surging, then finaly loses so much power that it stalls out. Takes forever to re-start and has to cool down a while first.

Here is what I have done so far:
- clean fuel tank, line, filter
- new plug properly gapped
- clean air filter
- New ignition coil
- Total carb rebuild with new throttle shaft and seals, new float, needle, and seat, gaskets, all the passages are squeaky clean. I do a lot of carbs so I know this one is set up right.
- new governor linkage and spring

I am about to buy it a new engine. This one is a 1990 build date so it's got a few hundred hours on it. But I want to try one more time and see if I missed something that would be cheaper than the re-power:

- Could this be a sticking valve that only gets bad when it's hot?
- Could it be very low compression (I have not checked compression)
- Could it be one of the safety interlocks shorting to ground when they get hot (assuming they are near the engine where they get hot)

I want to give it one more shot before I spend $$$. I can do a ring, valve, and gasket job pretty cheap if I don't need a piston or any real machinging.

Advice please!
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