can anyone help me?

[butchryan]

i bought a yamaha 1980 300 enticer, sled has sat for 15 yrs in barn. ran good for a while, then slowly started fouling one of the plugs. now everytime i put a new plug in that one cylinder the sled runs good for about a minute than a small backfire and then that cylinder stops firing. can anyone give me an idea whats wrong with it? i cant afford the money to put it in a garage. it was family owned and well taken care of.

[boats.net]

I know nothing about them, not sure what engine is in it but check compression, test ignition system and timing. Check fuel system to see if running too rich or too lean.