Sherco 125 2015. All of a sudden unable to select 3rd gear, 4th or 5th gear. 1st and 2nd, no problem. No obvious problem, noises. Any ideas appreciated? Thanks.

Shifter hitting anything? Other causes would be bent shaft or broken spring. Had had one that broke one of the pins on the end of the shift drum.

I'd be thinking something has gone wrong with the selector mechanism, Lineaway's comment about a broken pin on the end of the drum would be where I'd look first

Thanks, was out looking at the bike again this morning. Gear lever not hitting anything. It shifts in to 1 st and 2 nd no problem, but I noticed that if, when in 2nd, I push the lever down half a click it will then shift up to 3rd. Same procedure seems to work to select 4th and 5th gears. It seems to shift down the gears no problem. Does this description fit in with the advice in the above replies?

Thanks Shazsfan. How do I replace the spring?