Stock 2003 Ruckus (NPS50) w/ approximately 7500 miles, normally runs 34 to 35 mph on the flats (either at sea level or my 4,000 foot home elevation) is now suddenly much slower. Obvious loss of power after two recent incidents where it left me stranded at night in the rain (had to park it and hitchhike home). Both times it started sputtering and bogging and smoked a fair amount. Couldn't go forward at all while it would only idle roughly. It's possible I either got some bad gas or else diesel in the tank by mistake the first time it conked out; the station where I gassed up sometimes has diesel in the ethanol-free tank---and they could have spaced-out telling me when I said "$4 on pump three..." Both times I got it going the next day (siphoned out the bad gas/diesel before refilling with good gas) and managed to get it back up the hill all the way (although the 2nd time it still wasn't at all easy). Spark plug was black and oily; cleaned it well and also replaced the air filter and cleaned the airbox. Opened up the drive belt cover for the first time and discovered a lot of belt dust everywhere; blew it out with compressed air---but no noticeable improvement. I lubed the kickstarter which needed it sorely and at least it is much easier to start now. Today I opened it up again and replaced the original drive belt as well as took apart the variator bits and cleaned everything thoroughly. Possible clue to what ails my Ruck: My rollers were filthy and worn as suspected---they have some flat spots. I cleaned them with Simple Green and regreased the shaft (being careful not to get any grease on the variator pulley faces). The other clue is the fact that the clutch pads seemed pretty worn, as best as I could determine. They are both about 1/8th of an inch thick, perhaps a tad more but not much than that. I sprayed brake cleaner on them and the clutch pulley and cleaned that assembly as well before I put everything back together (including the new Honda belt). I really thought that the new belt would solve 90% of the problem but, alas, the power is still not there. I start out much slower off the line and gradually build up to 15-25 mph on flat or minimally uphill terrain. So does it sound like a clutch problem, variator problem or possibly still a carburetor/fuel problem? The engine revs fine now and doesn't smoke like it did when it conked out (I also later sprayed carb cleaner in the bowl to flush out any varnish crystals that might have been in there but none at all came out---the carb appeared to be fine from what I could tell). But the carb has never been rebuilt so the jets may be clogged for all I know. Would the engine run well if they were? The fact that it does run fine on the center stand is why I suspect the drivetrain more than the carb/fuel pump or filter---but I don't pretend to be any sort of expert on the subject. Any thoughts will be appreciated---I know I should at least replace the rollers but am mystified that the new belt (which was thicker than the old worn belt by 1/8th of an inch or so) and my extensive cleaning made little, if any, difference upon reassembly. I'm used to zooming around with WOT at around 30-35 mph no sweat but now my Ruckus seems like it just suffered a massive stroke or something. Help! PS: I will get new rollers or a whole new variator at some point (as soon as I can afford to do so) even if the cause is something else. Right now, I just want to hear opinions as to what is wrong---I'm stumped!