Craftsman 46" running VERY weak and rapid backfiring!

[Scottrw]

Hello, I've been having a miserable time trying to figure out what is wrong with my mower. Its a 46" Craftsman 21HP 540 CC Engine Model 331877 2371 G5 11020370. Its roughly 3-4 years old. Last week i ran over a long wire out ion the yard that was concealed in the grass. I immediately cut the engine and removed the wire from the blades. I did run the engine just to get the mower to the garage to be able to work on it, but did not engage the blades. Once the wire was removed I began to cut the grass again. Got about 1/3 of the rear yard done until I noticed the belt which functions the blades was rubbing appeared to be "melting." Again I cut the blades and just drove it to the garage. Just before getting to the garage it began to backfire and cut out just before I got it.

Now it will will start but sounds horrible..like rapid gunfire, and has very little power, I'm not able to get it to move at all. In looking through the forums here I've tried the following: New air filter, fuel filter, oil change, spark plug, cleaned the carburetor. Im now at a loss of what else to do!

Thanks for any help!

 

[motoman]

The wire may have momentarily bound up the rotation of the blades bending or breaking the "key" that keeps the flywheel aligned with the crank shaft which puts the spark at the correct point when the cylinder should fire. Many cases on this forum. I am not familiar with your exact model, but on my 24 Intek you can remove shroud exposing a big hex nut which must be loosened . Once off the key is visible. To the experienced eye it should be sitting intact , half in the crankshaft tip recess, half in the flywheel recess. Even a little deviation will throw off the timing. If this has happened you will have to pop the flywheel, realign and put in another key.