Is there a good replacement controller for Kollmorgen motors?

Howdy Folks,

I need advice on the Kollmorgen 400w motor. Does it have any overcurrent protection? I've heard that the controller fails easily and I'm afraid this may have happened. It is in a go-kart I built for kids. The kid and kart weigh about 150 pounds together and it is geared for a top speed of 15-18 mph. It started to lose power and quit after about two minutes of running. It no longer works and it draws quite a bit of current when power is applied and its at idle.

The test driver afterward mentioned something about having to use the brakes to bring the kart to a stop. He seemed to be saying that the throttle was stuck but it was hard to get a clear answer. When you're test driver is only 8 years old you don't exactly get the kind of technical feedback that you might get from Michael Schumacher. So he may have been sitting there with it power-braking for a minute while we were talking about the kart. When he tried to go again it just sort of crapped out. The motor only got slightly warm. I think the controller blew, but when I take the back cover off I can't see or smell anything fried. But I think it's toast anyway.

Can anyone tell me of a controller that would work as a replacement for the internal one? Something that is more robust but doesn't cost more than the motor? I'm running it on 24 volts.