I've owned this ski for a couple years now, it is in incredible condition and ran great until the tempo fuel lines clogged the carb filters. I replaced all the lines and filters and now it is missing at low rpms. Runs great over 4300 rpm and goes 60 mph but under 4000 it sounds like it's popping out of the exhaust. It will take off from a dead stop like a rocket but not if trying to increase speed slowly. I also tried new spark plugs, any advice?