My 2018 Cforce 500 HO continues to overheat. Last time the top of the piston had carbon and the cylinder walls had dark staining midway down. Cleaned it up and turned down the fuel controller. Replaced the thermal switch in the radiator. Did a radiator relocation kit to keep it clean, put the top end back together with a new head gasket. It was staying at 2 bars, the radiator was getting hot, the fan was coming on. It was keeping it at 2 bars temp. 5 minutes later it got hot and blew the head gasket for the 3rd time. I guess tear it down check to make sure the surfaces are straight, check thermostat, water pump, temperature sensor. Anything else you can recommend?