If your Troy Bilt lawn mower isn't working properly, there are a few things you can check before taking it to a repair shop. First, make sure that the spark plug is clean and in good condition. If the spark plug is fouled or damaged, it could be the reason your lawn mower isn't starting. Next, check the air filter to see if it's dirty or clogged. A dirty air filter can restrict air flow to the engine, causing it to run poorly. Finally, check the fuel level in the tank to make sure there's enough gas. If none of these troubleshooting tips solve the problem, then you may need to take your Troy Bilt lawn mower to a qualified repair shop for further diagnosis and repairs.