So today on the way to and from work my bike jumped in to neutral a few times causing very high revs and a nasty crunching sound. It is when I change gear up in the higher gears.
Any ideas what this could be?
The first thing I check whenever shifting problems occur, is the shifter linkages. The pivots and seals need lubrication. When dirt and grit gets into those points, they get sticky and hang up.
Pull the boots back, and wet each ball joint with white lithium grease, and spray the rubber gasket that the shift shaft passes through into the transmission and see if it starts behaving.
Make sure there is nothing bent, as well. Then move on to the clutch cable and make sure it has free movement as it is meant to... lubrication here as well, inspect for frayed cable ends, and proper adjustment.