sounds like either a broken recoil spring or a bad clutch
get a new one
Try pulling out the spark plug and clearing the cylinder
starving for fuel
dirty carb bowl or water in the carb
because ur car is deaaddd mate :)
Blocked air filter, need spark plug replacement,
The cams are worn down to far.
did you check and make sure you have plenty of oil. or maybe your lawn mower just needs a break.
make sure the gas valve is turned on and you put the air filter in right
your electric motor(I assume) probably wont have enough torque, That is on a Riding type mower, not a push mower, it might work on a push mower as long as its not self prepelled, because your motor probably still wont have enough torque!
replace it
bad bearing