Ive been having problems with my starter motor since rebuilding the engine last year and have ftried lots of different things to cure it. My downpipe on the exhaust is unusally big (3 inch bore) and is quite close to the starter motor. it is however wrapped in heat tape so it doesnt dispurse as much to the starter motor. Also ive covered the starter motor completely in reflective heat foil but when the car goes for a journey longer than and hour i have to wait for it to cool right down before it starts again.

The starter is not even a year old but i wonder could i have damaged the solenoid with the heat before i applied the exhaust wrap and reflective foil?

Any help would be great please guys as its really annoying?