Hi guys, new here. I have a 91 NSR250 that just stopped running as I was driving. Has fuel to the carb and cylinder, I pulled the plug to check for spark and when I grounded the plug to a cylinder head there was spark and then bike started and ran on one cylinder. I put the plug back in and no joy? Pulled the other plug out did the same spark check and same thing, the bike starts with one plug out and grounded/ Whats going on? HHEELLLPPP!!!!