My 2cycle ski doo 440 keeps fouling plugs hmmm.what is the problem here.the plug on the left is oil fouling .

[pro_ccna]

Its a 1977 tnt 440 runs great with new plugs,i can drive it around for 30/40 mins.afrer i let it sit i go to restart it and only the 1 cylinder will fire.if i put a new plug in away i go .I mixed the fuel a little on the light side but it doesn't seem to help..at idle it seems to miss just a tiny bit but doesn't seem like it would affect anything.when i ride and then check both plugs they both seem to be full of oil but ony 1 is fouling....whats up !!!!!!!