Is the gas cap vented on my fs100 or is there a vent line? After 5 minutes the rpms start to rise if not at full throttle and if you let off you it will die. Then starts hard. After pulling for what seemed 100 time I decided to top off the half full tank. It started the first pull. Ran fine for 5 mins and rpms rise. I loosen the cap and things are fine runs great. That night I replace the gas cap with an old one from a parts fs100 in the garage. Now thing are fine for about a month. Yesterday it starts again. This has me baffled should I replace the gas cap again or is there a fuel vent line thats plugged?