Developed to address one of the most frequent problems with fun karts, lubrication of the clutch bushing. This lube system supplies lubrication directly to clutch bushing through the keyway of the engine crankshaft utilizing a special zerk fitting. 12 Tooth 3/4'' Bore 40/41/420 Chain The SS series is the most popular style clutch used by the O.E.M.since its introduction in 1970. This clutch comes in many different configurations to meet any O.E.M. requirements. Set screws and key are not included. Use AZ_8454 key. Set screws not recommended. 10 Tooth - 3/4" Bore - #40/41 Chain Know your gear ratio! An acceptable gear ratio for a 12T #35 clutch would be a 60T or larger rear sprocket. A 10T #41 clutch would need a 50T or larger rear sprocket. Vehicles with rims larger than 6" or tires with a diameter of 14" or larger should upgrade to a belt drive TAV system.