I had a problem with mine earlier this year it started spitting and sputtering occasionally then got worse. one weekend it was so bad it started backfiring and with MUZZY exhaust it was incredibly loud. just for the heck of it I changed my plugs to NGK iridium and problem solved. IMO these things don't like to be ran at low speed or cranked up and ran for a short time then shut back off, that's when mine went from bad to worse really fast.
Brett- bought 10-11-15
'15 TERYX T2 LE, stock tires/wheels-for trails, 29.5 Assassinators on STI HD3 wheels for mud, 1" wheel spacers, SATV high clearance front/rear A-arms VIPER Elite 5k winch, Snorkels, Half Windshield, Bubba Rope, CIPA Mirror, LED backup light, APEX Battery, Kawie Billet Shift Handle, VFJ clutch, PC5, MUZZY dual exhaust.