I have just received a 1981 CX500 Custom with 110,000 miles. It was said to always run excellent, but has been in the garage for 4 years. I put klean in the tank, but when I go to crank it, it won´t start. When I spray ether in it, it starts to run timid but will not keep running unless I continue to spray ether in it. It has a slight knock on the clutch side. DOES ANYONE HAVE SOME ADVICE?