Why do you believe that 160 is too high? There maybe nothing wrong with your engine. If there are other Leopards at your track, ask them. We didn’t run a probe in the head of a Leopard but did have one on a Rotax. 150 to the high 160’s were acceptable water temps. Do not throwing parts at your engine until you’re sure there’s a problem. A spare pump, belts and gears are good to have as spares. Unless the gears are severely worn on their sides or the teeth are misshaped, there’s no reason to replace them. If they are worn, replace them and the chain. Another good spare for a Leopard would be clutch.
How are you purging the air from the cooling system? Are you removing the temp sensor and spinning the rear wheels until water comes out? We used to run the engine on the stand until it started to warm up. Then would tip the left side of the kart up so the radiator was higher than the engine. Make sure the pump was turning, set it back down and fill the rad up to the top. No need to leave room for expansion. The radiator cap is suppose to hold pressure and allow some water to escape if the pressure builds to high. Have a catch can attached to cap.
If the rear width is not at the max allowable, move the hubs out a quarter inch to free the kart up.
See you PM.
LAD Specialties customer / tony kart / rotax / kt100