A friend of ours just purchased a used 125 sherco, 2006 model year. We know the former owner, he never had a problem with this as far as we know.
twice today, the bike suddenly revved up SIGNIFICANTLY with no provocation, while ridden by a novice rider using very little throttle (once was a crash, once was a nice save by a very rattled rookie!); (Mike guestimates that it was sticking at, for example, 1/4 throttle ... and thus continuing to increase RPMs/accelerating.) (to be clear, I don't mean a simple small increase in RPMs like my GasGas does as it's running out of fuel ... this was a significant jump and continued to rev higher and higher)
then Mike (my hubby/our mechanic) rode the bike and eventually was able to repeat it. When it revved, he could snap the throttle several times until it shut back down.
no binding whatsoever at full lock either direction.
the throttle cable had a small amount of excess freeplay which he removed. still could make it stick and scream. cable is good otherwise.
We found that, when an adult rider is sitting on the seat-less seat area (not on the fender), the tank actually could pin the throttle cable. Zip tied the cable (loosely) to a segment of frame that keeps it away from said pinch point. Not certain if the bike reved out again after that adjustment.
Obviously, the new rider is nervous to get back on her bike, and Mike is nervous to let her ride it again until we're certain the problem is solved.
has anyone seen anything similar? any ideas what could be happening?