Hi, I have a 12.5Hp B & S vertical shaft engine in my mower and last weekend the plastic starter cog (the one rivetted to the underside of the flywheel) lost a few teeth and it would not start. So I replaced the cog with a metal one and reassembled it.

When I returned the flywheel I made sure the it was aligned properly on the main shaft and the key on the shaft and flywheel was inserted correctly. But when I try to start it, it won't fire. I have tested the spark and it appears to be OK. It looks a little weak but that could be normal.

I am pretty sure its not a fuel problem as I have also sprayed ether into the air filter and all it did was backfire once.

Apart from removing the flywheel and changing the big starter cog I have not altered anything else so I am at a loss as to why a motor that used to run fine now won't start.

If anyone can help with suggestions I would be very grateful.