On Feb 23, 7:19*pm, JM_newsgroups wrote:
Hello,

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?
Thank you!

Thanks,

JM

A very dirty air filter can cause it also.