Weedeater lawn tractor won't start w/key. I can jump from battery to solenoid & it starts. It also starts w/o depressing the clutch. Has new starter and new ignition switch. No loose wires. No blown fuse, battery OK. Used to start cold w/key but then when shut off it would not restart again after motor got hot.

I'd recheck that new ignition switch. You should have power going into the switch before you turn the key. Once you turn the key you should get power coming out on the way to the solenoid. Jumping at solenoid just bypasses the ignition switch so that is likely your problem.