Ok, here's what I've got. Any help would be appreciated. I have an '08 kfx 450r. It probably has almost 10 hours or around 10 hours on it now. I have installed a Two Brothers M-7 slip on exhaust, a dynatek FI controller, and a K&N filter. The only other modification I've made is I turned the air intake tube(on top of the air box) around to where I figured air could go straight into it. It seals right, Fits the same way just turned around.

   I went out for a ride with my buddies. I rode it once before we went out. I rode it around a few mins. It started sputtering. It was almost out of gas. I parked, the fuel light was on. I looked in the tank and barely had any left.  I am running the right fuel in it. I filled it up, then loaded it up for the ride with my buddies.

   When we arrived, I unloaded it, started it, let it warm. Started riding. about mid throttle and maybe less than a minute, it was sputtering/missing, had to keep on the throttle to keep it running. I stopped, let off the throttle, it shut off. I restarted it to take it for a ride while they watched. I took off and it was sputtering very little.

      I started hammering on it and checking it through mostly all gears and it'd sputter a little less. Then it seemed to be fine. We went riding for about 2 hours and it was great. Riding fairly hard. hill climbs and all. ripping and tearing.

     We decided we're done riding and start heading back. now we're more cruising than flying. It starts doing it again, this time worse. Stayed pretty bad the whole way back. It's like pushing in the throttle and having nothing then having it, nothing, having it, and so on. It shut off on me a few times trying to position it to load it. Still had to stay on the throttle. Shut off on me when I let off throttle again and this time it wouldn't start up. Spark plug was fouled and black. The first several threads and the 90 ground. Just coated with black, not thick or nothing.

     Is it just from running it too low on gas or do you think it's running to rich? Sorry so lenghty but I figured I'd help explain as much as I could. Please help... SOMEBODY lol. thanks