RE: Club FOX!
I'd go along with that Sport. My Foxes back in the 70's had to go through a "grind in" process it seemed before you could even worry about "break in". <GGG> Those poor things would belch black glop for at least a gallon. Maybe by the second season they'd be just about settled in.
The newer ones are much quicker to come in, although still not the motor of choice for the instant gratification sort of r/c'er.
My .15BB seemed ready to fly right out of the box. My .25BB needed a few tanks on the bench, and a few more tanks in the air before it wanted to play nice. It's a rocketship now....
The .40's seem to need a bit more massaging still. Nothing unreasonable, but some time on the bench is time well spent.
All this would be unacceptable if it weren't for the fact that the engines do in fact achieve a very nice running fit, that with minimal care (and good amounts of castor) will last for a very, very long time.