yz 85 fouling plugs

[wollywalton28]

i have recently just bought this yz and it needed a piston ring so i fitted a new one and it fires up fine first time . everthing seems spot on untill i go to ride the bike for about 10 minutes and the bike just cuts out? i checked and theres no spark. i have been through numerous plugs but aint sure the problem. any advice would be great thanks

 

[mideastrider]

It could be as simple as the plug being the wrong heat range. It could be a crankshalf seal gone bad. May be the fuel mix along with jetting. Any clue what the prevouis owner was using for fuel, type of gas and oil at what ratio?