When I did run my old Jerobee, way back in the 70´s, I remember that it always ran a bit warm/hot when the needle was near the limit.
I have now added a little cooling fan as seen in this picture.
It is the type and size as they use on modern speed controllers for electric RC cars.
It runs on 5v and the cooling is fantastic!
When I disconnected the fan in a middle of a run, the engine sounded overheated after about 30 sec, I stopped and connected the fan and it went back to normal again.
