Help with mower issue please and tia

[cbrjuly380]

Hi I have a husqvarna yth1842 with a B&S 18.5 intek engine(33R777-0003-G1) I put new pulleys and spindles on it last week, it was running and mowing great until Sunday and it just died while my Mom was mowing. Now it won't start,it turns over but when it kinda cranks it sounds like a small caliber semi automatic rifle lol It just spits and pops then of course dies? Other times it backfires through the air filter. So I checked and cleaned the carburetor it looked okay,checked the ignition coil (magneto) it was okay but I did notice that brand new spark plug was black when i took it out? Is it the gas maybe? TIA

 

[slomo]

Check flywheel key.

 

[cbrjuly380]

Check flywheel key.

Okay just remove the top cover and then remove giant nut/bolt I'm center correct?Will I need to buy a flywheel puller?

 

[slomo]

I use an air hammer and a long pry bar. Couple zips and she is free.

 

[slomo]

Hope you find a bad key. The next likely fix is the camshaft.

 

[Auto Doc's]

Pull the rocker valve cover and see if it bent a pushrod. Let us know what you find.