jets have to be adjusted according to the engine too big its too rich ( bogging out ) too small then its too lean ( seizeures) keep to the biger side its safer, There are two ways of transmission work basically in general, you can have a weak tension spring with light rollers and weak clutch springs OR strong Tension spring and strong clutch springs and heavIER rollers. its all personal preferance and depends alot on the track set up as well .