lets first confirm what ya have, i'd suggest strongly to not run it till you check that main jet, it should be at least a 270,
you'll need to pull the carb, carefully remove the 4 screws to remove the bowl.....
proper size phillips screwdriver, lots of downwards pressure, turn slowly, they strip out easily
after getting the bowl off, the main jet will be right in the center, with a white plastic slash gaurd over it, 6mm socket.nutdriver will reove it, it will say on the side or top what size it is
report that to us, and i'll work on some homework for you