I have a troybilt 42in cut mower it turns over but does not start. I can but gas in the carb and it starts fine. I have checked the lines and everything and it seems to be getting gas.

This normally means that the carburetor needs a good cleaning. The other thing you might want to check is to make sure the solenoid on the bottom of the carb is working properly. If it's not working it won't let gas into the engine.

Agree, sounds like the float/needle is stuck or the solenoid underthe bowl is not working. They added these solenoids years ago to prevent backfiring and they can fail. I found my wire had vibrated off last summer

I'll also add, that this (the gummed up carb part) can be eliminated or at least delayed by years if the last time you use it in the fall, you let it run until the tank and float bowel are dry.

Storing it with fuel over the winter will cause this. Fuel stabilizers will help but I like the Dry system storage best.

I have a Motorcycle that gets annual use but sits for most of the year between uses. I've not had the carb apart in that but once in almost 20 years I've owned it. And when I got it it was parked for 7 years with a full tank of gas. That mess took 3 days to clean out.

I have a nice selection of garden tools from several mowers to a Chipper shredder and several generators that I picked up on trash day that had no other problems but a gummed up carb.