spongehead wrote:

I have an old Briggs and Stratton 3.5hp push behind lawnmower and the
idle revvs up and down constantly. Never idles normal. The spring on
the shaft idle looks good. Any help on what this might be would be
greatly appreciated.

Hi...

Happens that I have one; as well as still have the manual...
hard to believe 'cause it's about 15 years old

Anyway, still runs perfectly, so I'd be happy to take a couple
of pics of the springs and carb linkage etc, and mail them to
you if you like?

Could also scan the applicable pages of the manual if you
think it would be helpful.

Take care.

Ken