If anyone else is having trouble fouling plugs on the 426 I have found the solution that may work for you. First I changed the plug to an NGK CR7E. Second was I always turn off the gas and let it run for a couple minutes periodically reving it to burn off the excess gas. Third but not least is NEVER EVER EVER no matter what DO NOT give it gas while trying to start it. These simple steps have helped me have the same plug for a month where I use to change it every ride.