Clutch adjustment and operation for a Yamaha KT100 engine is a large factor in lap time improvement. The disk clutches used on KT100 kart engines are designed to allow the engine to operate in an rpm range where overall acceleration is maximized. Here are a few tips to make sure that your clutch performs as well as it can.
- Lap the clutch hub to the taper on the crankshaft. This maximizes the contact area between those two parts and reduces the possibility of the clutch hub slipping on the shaft and shearing the key between the two.
- Do a trial assembly of the clutch on the crankshaft to set the drum end play to the manufacturer’s specifications. You will need at least .005”. Try not to go more that .015”. More end play will work for a while if in a pinch, but engagement of the clutch disks with the drum may become marginal.
- Verify the air gap between the clutch disks. Within the limits set by the manufacturer more air gap allows higher clutch engagement rpm and less air gap allows lower clutch engagement rpm.
- Measure the runout of the starter nut where it fits into the support bearing. A range of 0.000” to .003” is desirable. Up to .006” is acceptable. Depending on the starter nut used, the run out may be adjusted by machining the starter nut or aligning the engine crankshaft.
- Set the stall rpm to slightly below the engine’s peak torque rpm. This is done with the spring preload adjusting screws. Tighten or loosen the springs’ tension equally to achieve the desired stall rpm.
- Setting the stall rpm is done at the track. Do a preliminary adjustment with the kart on the ground and driver in the seat. Read the tach while holding the brake to lock the rear axle and applying maximum throttle for 2-4 seconds. This reading is the stall rpm. Adjust the spring tension on the clutch to the desired stall speed. Test again and repeat until The recommended stall speed for each version of SRS KT100’s is in the webpage instructions for that engine.
- The final adjustment is made while running on the track. Note the clutch stall rpm coming off the slowest corner. Adjust the spring tensioning screws to achieve the desired stall speed.
