It runs fine for 15 minutes, then every once in a while when I open it up, it cuts out, then after 20 min it gets a little worse, and after 45 it barely runs, it cuts out and dies if I twist the throttle more than 5% but then it fires right back up. Here's the weird part, if I turn it off for 3-4 minutes it starts back up and runs fine again for about 10 minutes. I replaced the piston with Oem parts and spark plug about 10 hours ago, it ran fine for about 8 hours and now this. Valves are good, I took the fuel pump apart to where I could see the filter and it looked clean, but there wasn't really much to see, the injector was spotless, as far as I could see. At first I thought it was the air filter because it happened during a moderately dusty race, but I changed it out and it still did it. The gas is new, but when it started happening it had 3 week old gas in it. Maybe that gummed something up. I ran an ounce of seafoam mixed with a gallon of fuel all the way through it then filled it back up and ran it a little more but nothing is helping. Any advice is appreciated before I go spend 450$ on a new fuel pump and injector for the next race in 7 days.