I was translating a documentary called American Loggers. In one of the episodes the crew have an accident in the woods and their forwarder breaks up so they try to tow it, however, the brakes are locked up. The mechanic tries to fix this problem but fails and he says "That thing’s pretty heavy, dude. It’s pretty heavy and it’s hydra start. And the oil in the hydra start’s cold and they ain’t nothing wants to turn, you know?" So, what does he mean by "hydra start"?