Change plugs every spring, alway sta-bile gas and run before storing. After trolling for 1/2 to 1 hour and I start to trottle up slow but steady,(not tromp on it) when its up to around 1/3 to 1/2 trottle(sometimes) it will start to miss and shake and naturally won't excelarate anymore , but if I back off the trottle and retrottle back up it will clear up and run perfect and also idles and starts fine. I also drained the carbs and the tank and made sure it was clean ,changed the fuel filter and put in fresh premium gas .