Today I started er up and it backfired, then started running on only one cylinder. It has been running like a top for the past 2200 miles(it had about 7200 on it when I got it). Is this likely a plug issue, and is it the first thing you would check? Also, the majority of my riding is under 50 mph...would you recommend going to a hotter plug? The manual does say you should use a hotter plug if you do a lot of low speed or cold weather riding. I take it that <50 mph qualifies as low speed riding.