I have a Yardman lawn mower with a tecumseh 4.5 hp and it won't rev up. It starts fine. It has an automatic trottle and if you manually try to rev it up, it will stall.

ray, June 2008

I just had the same problem with my snow blower, it would idle, but when I would try to rev it up it would spit,sputter,backfire and die. I put a new carb on it and that didn't help. I ended up taking the flywheel off and found the key that holds the flywheel to the crankshaft was worn enough to allow the timing to move, inturn causing it not to rev up. I put a new key in and that fixed the problem. Runs like a champ. Hope this helps

bearclaw, February 2011