About three weeks ago I bought a used 2001 Husky 50J for my son. Overall I am very impressed with the bike but it seems to have a consistent problem. It starts and runs great when cold. The following has happened the every time he has ridden it for any length of time. It has happened after as soon as 10 minutes and after as long as 45 minutes but it is always the same. The bike starts running terribly and eventually won't even keep running. It will start but backfires and has absolutely no power. The first time, I let it sit for about 10 minutes and it started right back up and ran well for the rest of the day(about 90 minutes). The second time I changed the plug immediately and it started up right away and ran well the rest of the day (again about 90 minutes). It happened again today. It is getting annoying and I'm starting to not trust it. I have always checked the plug when this happened and it has always looked just like I try to get my plugs to look but changing the plug yesterday obviously helped. He is riding the bike at a pretty good clip, not boggin it or running at low throttle for any length of time. I realize that there are a million variables that could be causing this problem. The stock plug is a B7HS. I am running the same mixture that I run on my KTM300, Amsoil at 50:1. I did buy it from a dealer and plan to speak to him about it but I just wondered if this sounded like a problem that anyone else has had. I seem to remember a post a while back that mentioned a coil or stator problem on these bikes. Would this cause it to act like this. Any help would be greatly appreciated.