Well, I had my first problem with my 2000 400EX. I went riding on Friday with my frined, he has an RM125 dirt bike. We were riding trails for about an hour and a half, then we went to a big circle track. The track was big enough to were I could get into 5th gear on the straight aways with my 14 tooth front sprocket, then I would power slide the corners in about 3rd gear. I was riding kind of hard nothing out of the normal. Well after about 15 mins of riding my quad would start to cut out in the straight aways when I was in 5th gear going fast. It was acting like it wasn't getting any gas. I pulled over and checked everything gas and oil everything was full but I put the tank on Reserve anyways to make sure it was getting fuel. I then started to ride again and it was still doing it in the straight aways. I then stopped for 15 and let it cool down. After that I putted around in 3rd gear slowly to get some air to the motor I thought this would cool it faster. I then stopped for 15 more mins and let it set. Then we went and rode trails. It started to cut out in about 4th gear pinned. I stopped and told my friend I was done for the day and I slowly rode back to the truck. I got home and stripped it down, changed the plug, the used one looked normal, cleaned the filter blew out the gas line from the tank to the carb thought it might have been blocked with something. Took the carb out and pumped the throttle and the carb shot a nice stream of gas like it is suppose to. I put everything back together. Started it in the shop sounded fine, throttle response was fine snappy like normal. I didn't ride it though. So why was it cutting out? Its not my jetting because I have had this quad for 7 months and it is fine. I have an R4 exhaust it is jetted for the KandN and the R4 I am postive it is jetted right. I thought it might be the gas but it is the same gas I always run 92 octane Amaco gas. I bought this gas in Iowa and I usually get my gas in Nebraska do you think this gas might have had some water in it? I didn't see an inline fuel filter on the 400EX does anyone recommend putting one on? Do you think it was overheating? I had oil and like I said I was going pretty fast, plenty of air was getting to the motor and oil cooler. Their was nothing blocking my cooling fins on the motor. Anyone have any ideas? This is the first problem I have ever had with a Honda.