Riding lawn mower will try to turn over but will not start.

Disconnect the kill wire from the plugin. If mower runs, then it's in the main switch, or one of the abundantly, redundant safety switches on the mower. (Seat, clutch, blade engage, etc.) HOWEVER, I have repaired many mowers that the kill wire from the coil, would have burnt insulation, sporadically grounding out the coil. Check for the simple things first, I always say.

I have fixed about 99% of all safety switches by pressure washing them (not a blaster, but a smaller electric washer), then they come to life. After that, you force a good solvent (WD40 is fine), let her soak for a few minutes, then blow it out. Afterwards, I will spray electronics cleaner/lube into the components to insure a long life.

Where is the kill switch located

Hi,
There is a usually white or yellow wire that goes beneath the shroud and it the ignition ground. It could have two ends that plug together or a flat blade and plug that connect. At any rate unplugging this connector will separate the engine from the frame and steer you to your problem.
Peace,
Clarke