On Sat, 23 Feb 2008 17:19:41 -0800 (PST), 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?

The governor would be a candidate. I had that with a broken governor
spring.

G