Wifes cousing just bought a 96 XCR 600 tripple. When it idles it is fine. When he rides the sled and a good rate of speed, coolant starts shooting out of the overflow cap hole. The sled was well taken care of by its previous owner. It has 2,500 miles. The temp light has never come on. The overflow tank is NOT over filled I made sure of that. We did all we could to relieve the system of any air bubbles, but this didn't help. The sled still acts like old faithful. Could this be as simple as a bad radiator cap? Are these fairly common to fail? Anything else I can check for?