Make sure you have fuel getting to the carburetor.
Pull the line from the carburator and turn the motor over, Gas should come out of this line
Check the spark plug for sign of wear and tear. Some spark plugs can foul even after 5 minutes of use
Try using starting fluid to aid the starting process, spray a little into the carburetor.
If it starts by spraying starting fluid and dies as soon it runs out of starting fluid then this means there is no fuel getting to the engine. Check the carburetor.
or there might be vaccum leak in the piston area. If your piston is badly scratched up due to the lack of oil, then you may need to replace piston and rings to regain compression. Intake tappet adjustment can be made to increase compression
