Well... I thought long and hard and fired it up with the new blade in place. Ran like a charm... not much more vibration than usual. I started to mow. About two feet into light, fairly short grass it started to "ratchet" so bad it scared me.

My new mower is a Yard Machines with a 4.5 B & Stratton on a 20" deck. $170 at Crappy Tire. It's light and that should be good for my back. PLUS, I am 99% sure I can change out the motors and I'll probably do that this winter if the new motor works well the rest of this season.

Oh, yeah. The valve cover has shiney duct tape on top of it.