I have a base-level 3.5 HP Briggs & Stratton engine that's about 6
years old. It's a throttle-free design with a primer bulb. Lately,
after I get it started, it goes in to a rhythm of racing and dropping
off about every second. This started rather suddenly. The plug is
OK. I started to take it apart, because I didn't even know if mowers
had "points". I assume it's some kind of induction ignition system
based on the setup of the cutoff switch and the magnetic flywheel.
The carb looks like nothing more than a plastic throttle body, and I
don't see a float/bowl of any kind. I generally don't repair mowers,
obviously. Does anybody recognize that surging/dropping behavior?
Thanks, gentlemen. I had pulled the cover off and cleaned it. The
air filter, governor, and the air-controlled assembly looks OK. I
reassembled and had the same problem. I'll give Shopdog's suggestion
a try, because I had seen that mentioned for another B&S motor. The
condenser was kind of funny to reinstall, because there is enough play
to have it stick right to the flywheel.
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