I desperately need help locating exhaust valves for my 1989 KX250. The local agents have stripped the head, re-plated the barrel and now tell me that they can't get new exhaust valves. This after quoting me R6800.00 to do that repairs and asking for a 50% deposit upfront. This was almost 4 weeks ago now and I am no closer to having a working bike. Does anyone know if the valves form any other models can be used? Does anyone know where I can try to get these spares from? Any assistance would be greatly appreciated.