I have a 2013 yz85. I has just rebuilt the engine 17 engine hours ago. I changed the spark plug and put it away. The first ride with that plug was weird. It ran really rich after warming up, then popped three times and shut off. I pushed it home and looked at the plug, my plugs are usually golden brown, but instead there was just oil color on the small arm that goes over the middle of the plug, and the rim of it was dry, but no signs of detonation or running lean. I put a new plug in it and it fired right up and ran perfect. Was this just a problem with the plug or is it my bike?