Gasoline fueled internal combustion engines are not rocket science. Three fundamental things are required to run. Air, fuel, and spark all in the proper amount and at the correct time.
Fuel must be introduced into the incoming air stream at a ratio of approximately 14:1 air to fuel.
Edit: I first wrote 14% fuel then realized that was wrong. It's been a long time since I've used math any more complicated than addition and subtraction but I think a ratio of 14:1 is about 7% not 14%.
Compression of the mix occurs as the piston rises in the cylinder with valves closed and a spark is introduced at or just prior to top dead center.
When you floor the accelerator pedal do you see black smoke from the exhaust?
If yes the engine is being over fueled or intake air is blocked.
If no, the engine is fuel starved.
This most often occurs due to machine being parked or not used for long periods of time with the braindead congressionally-mandated ethanol gasoline. The fuel tank, fuel lines, and injectors may be fouled or the fuel pump is not pumping adequate supply of gasoline, or fuel filters are blocked.