I am working on a trailboss 250 r/es for a friend and have ran into a stumper. The bike is a 85-88 model, it has 120 psi of compression and holds it pretty long so i know the seals appear good in the bottom end. It has 2 gallons of new premium gas in tank and good on oil and a brand new plug i got at the dealer. my problem is that it will only run on ether and not the gas  and it seems to crank along time to start and run at all. Any info?