My sons Wolverine runs great when accelerating but once it reaches a cruise it's starts to sputter. It's even worse when you back off the throttle a little.
We checked the spark plug colour and it's rusty brown so I don't think it’s a mixture problem. The quad has a SuperTrap muffler with 12 plates and a K&N filter too, other than that it is stock.
Any ideas?

 

did you rejet?
mine ran well with the k/n, 155 mainjet kit, and megamax with 12 discs, but sputtered or missed at cruise.

I put a smaller jet 152.5 in and it took care of the prob.
I've heard it's too hard to judge mixture by the spark plug because of oil additives.

Check the jetting.

 

Yeah its your jetting dude, you should have rejeted when you put the Supertrapp muffler and the K&N on, try goin down to 152.5 on the main jet like MrWolverine said, and you shouldn't have any more problems!!!!

 

Thanks for the input, we have been rejetting and thought it was OK. Come to think of it the problem arrose while riding at 5000 plus feet and the jetting was done at 2500 ft so you may have something. We will check it out and let you know the results.

 

It is running lean. With the supper trap you should not have to rejet. But with the combo it would run lean. IT is not like a 2-Stoke, runs great when lean, but 4-strokes run like crust when they are lean.