I have a B/S 16.5 OHV Twin (Commercial model). Generally speaking it starts as soon as I hit the key. Today when shutting it down it backfired twice (two different occasions) but started normally. When I went to start it to put it in the shed no luck. Doesn't sputter or backfire. Changed the plugs, spark is not as strong as I would like (plug grounded on block), but should start the engine. Tried starter fluid down the venturi, no luck there either.. help.:confused:

Charlie

Things to check are the valves (are they in spec?) and the flywheel shear key (have to take the flywheel off to check).