hi i just bought a 97 scrambler 400 4x4, it ran great then while i was riding it , it started sputtering and died . hasnt started since. but when i pull it over it backfires through the carb and puffs smoke out of the breather. but it only does it about every 10-12 pulls?? ive cleaned the carb, put new plug in and a new uni air filter. could it be the cdi box? or stator? someone please help

 

Welcome to the forum! Pull the valve cover and check the exhaust cam lobe! 1996-2000 model 425 and 500 engines had a run of soft cams and the exhaust lobe would wear down along with grooving the exhaust rocker arm. I replaced many cams on these year models from the early 425 and 500 Rangers,Sportsmans and Scramblers,etc. The major symptoms were what you're describing,popping back through the carb,idles but won't take throttle,etc. IF the exhaust cam lobe is elliptical like the intake lobes,then may just need to adjust the valves. .006 clearance on intake and exhaust from TDC. To adjust the valves pull the cam sprocket plate on the right side,pull the recoil and when the intake valves go down and comes up,then turn slowly until the cam sprocket index pin lines straight up center of the head (this is TDC) Then check valve clearance and adjust if necessary. This may OR may not be the problem,but sounds like it. If this is NOT cam related,could be carb,fuel, or electrical related? Hope this helps you get started and keep us updated OPT