RE: Official Hyper ST thread!!
That macstar .28 engine runs hot. I ended up burning mine out. Are you running it with the body on it? If so, have you cut a big hole in the front windshield to cool the motor? Also, be sure and check to make sure the fuel tank lid is properly seated after refueling, or you could develop an air leak which will cause you to run hot. I push down on the fuel lid to make sure it has a tight seal. Removing the shim is no big deal, in terms of difficulty. Just be careful not to stip the hex screws when removing the head. Removing a shim will increase the engine compression because there is less space in the compression chamber after the shim removal. I don't understand how that would decrease the engine temperature, though. But, I don't know much about it.