Luis,
One quick way to check the fuel pump is to take the bowl off the carb and crank the engine with the mags OFF. With the bowl removed, gas should pour out the bottom of the carb as you crank it. Another way is to unhook the fuel line at the carb and crank the engine, switch off, and see if fuel is coming out of the fuel line while cranking.
Do you have a primer system on the motor? If so, you can start the engine with that. The primer bypasses the carb and puts gas directly into the intake manifold.
Are the fuel lines and fuel pump full of gas? Sometimes, if they fill with air, the fuel pump has a hard time starting the gas flow until the pump and lines fill up.
I doubt it is a timing problem. That is almost impossible to change accidentally. For some reason, you are not getting fuel to the engine.
Bill.
