My son's 360 has a problem that so far the Kawi dealer hasn't been able to cure. When being used fairly hard, (rode in the snow, pushing some snow) it is coughing and sputtering sometimes until it nearly dies out. I've found it to happen in two situations with two different results. When stopped and idling (or turned off) and then going again it will cough 2 or 3 times and then run ok. I've also found that when run hard for a distance it will begin to cough and sputter until it nearly quits and then suddenly (like you flip a switch) take off and run normal again.
The problem has occured at an elevation of about 7500 feet. The dealer has rejetted the carb for this elevation as well as shimming the clutch. The air filter is clean and fuel is 91 octane and I don't think it is icing up with the temps it has occurred. The engine has less than 30 hours and around 300 miles on it. I've checked the gas tank vent line and it's clear, tried running it on both the on and reserve position on the fuel valve, tried pushing the reverse over-ride button when its has sputtered, tried partial choke, all without any positive results.
Any help would be appreciated. So far the warranty has paid the dealer, but it is about to run out and I'm hoping to figure this out before it's gone.

 

Wish I had an answer to the problem for you. But to answer whether I've experienced it...YES. I ended up trading my p360 for a p650 because of all the problems I had. One of which was the sputtering for no reason. My main concern was that it was happening on hills, very steep hills, and it would happen near the top and I would have to roll backwards, regardless of what was behind me!! It also happened on flat ground where I would be going at a good speed...all of the sudden it would 'sputter' and launch me toward the handlebars, then it would work and throw me back. It $ucked. Basically, it did exactly what your son's is. It happened MANY times, it just kept occuring at odd times (odd times to me, maybe not odd times if you know what's causing it). But I did notice that it didn't do it in colder weather. It mainly happened when it was hot out, and a lot of the times after I had shut it off for a while (15-30 min) and then hit the trail again. I wondered about vapor locking but we tried all that would stop that. The mechanics and Kawi had no answer. One of the mechanics did say that he had a problem with one having a floater in the line that would clog it up and cause that. But that wasn't the case with mine. I hope you or the dealer finds the answer before your warranty is up or even just so you can fix it. My experience is that it doesn't just go away!

 

Has anyone checked the float level in your carb?? Sounds like it could be your problem. If your float level is set to high when you are hard on the throttle the float won't drop down far enough to let the fuel flow into your float bowl keep up to the demand you engine is making, this can also occure when you are going up a hill the float closes off the fuel supply because of the increased angle of your carb. I can't remember what the messurement is spose to be but it doesn't really matter what the book says you just have to set it so it works for you. Your level is messured by taking your carb off, removing the float bowl, and slowly turn the carb over until the flange on the float starts to put pressure on the needle, you then take the messurment from the mating surface of the float bowl to the carb boddy to the bottom of the float. You adjust it by bending the tab that contacts the needle. Might be somthing to check.