On Mon, 12 Jul 2010 00:56:54 -0700 (PDT), Hustlin' Hank wrote:

if you drilled holes in the flywheel you may have knocked it out
of balance. Check balance before re-assembling.

The holes in the Briggs and Stratton 3.5 HP engine flywheel are pre-drilled
by the manufacturer. All I needed to do was tap them.

I don't think tapping the two holes (1/4x20) will knock them out of whack;
do you?