maybe y'all can help. i have 650 triumph tiger - single carb, boyer ignition and 6v coils. without fail, i seem to foul the plug on #2 every time i ride it. i've tried cooler plugs and hotter ones..... same result. it doesn't smoke/ burn oil and is timed right. my only guess is that it's valve related since it's a single carb bike and #1 is just fine. any ideas / suggestions?