Sounds like a clogged carburetor or filter. Start simple.
Compression test is always first.
Spark to all cylinders.
Check primer bulb and line
Check filter on motor.
Start motor. keep choke on or half-way on after it starts.
If it stays running with the choke on and it dies after you open the choke, its starving for fuel.
Pull carb. Disassemble. Clean. Re-build. Re-assemble. Re-install. Start up and adjust to specs.
Take a ride dowen to me and I'll be glad to do the job.
Capt.Matt