Here are some video examples of a stock machine clutch calibration stalling on hills and needing a helping hand to get moving again. The clutch is slipping because the engine is not making enough torque at that low RPM to keep it locked up. The result is stalled forward movement becoming a dangerous situation.
As any snowball effect, the clutch slips and gets hotter and causes it to slip even more...
http://www.youtube.com/watch?v=Ue5wl...eature=related
Notice the rear tires are NOT spinning, and he has the throttle pinned... it's just grunting going no where.
http://www.youtube.com/watch?v=u1Zxp...eature=related
Another with the engine lugging way down under load, barely getting it done... not very exciting or responsive.
YouTube - MOV01662
This same scenario is what was happening to my Wife on steep hills in PA, leading to my clutch research. Her 250 eventually stopped forward movement all together and then what? Reason for the busted up / stitched rear fender... Lucky the only thing she hurt was her bravery.
http://www.youtube.com/watch?v=jtl1t...eature=related
Listen to the low lugged RPM of the stock clutching during the donuts in these vids. Very subtle and not very exciting and not making much power. Almost sounds like it's gonna stall out if it grabs hard enough... The rear wheels actually stop spinning at one point in the 2nd vid.
DS250 in snow - YouTube - Truveo Video Search
DS250 doing donuts in snow - YouTube - Truveo Video Search