Please ppl I am on vacation! Ok so my girls has a 03' 636, it has had something wrong with it for a month now. It started on the highway at about 80mph 6th gear her bike cut off she pulled to the side and once she was able to get it to first it started again. The very same day it hapened again on the way home. Wierd but ok. Thaught it was one of the sensor's (kickstand or clutch) Then about 3 days later she gets stuck in 3rd gear on the road and has to fight it back to 1st. I thaught the oil looked dirty so I changed it. Started up and no it was the same no problem starting but gears were still sticky? You really got to push that sucker down to get to first! Ok so not fixed. Saw the chain had alot of slack so thaught maybe, so adjusted slack on chain only an inch 1/2 now
Ok so chain didnt help, now I cant get outa first only N and 1st and its hard to get into either one. Thaught ok maybe clutch cable has to much slack adjusted it! NOTHING! Please help im on vacation and we were gonna go for a long ride but cant fix her bike! Got 4 days to fix and go and im stumped!

 

Sound like a loose battery terminal or corroded connection if the just dies all of a sudden. Check them and clean & tighten. The shifting is another problem. It's very difficult to get these in second gear if the bike isn't running and rolling.

 

sounds like a bent shifter fork inside the tranny to me. make new plans is my suggestion.

 

Good point on "is the ride rolling" when these shifting issues occur.
Have you replaced the CS recently?

 

these bike are hard to shift from 1st to 2nd but u should be able to shift from 1st to neutral with ease and for as the bike cuttin off check the side stand switch and battery terminal if they are loose

 

as for the bike cutting off what about the gas tank vent tube being kinked, can t that cause it to shut off also