My 2005 S50 shifts rough or not at all sometimes. No pattern as to temperature or clutching. ???

 

Did you buy this bike new and has it been resolved yet?

 

Had an issue with my S83 Boulevard beginning to give me shifting problems.
Turns out, the shift linkage needed a shot of WD40 or silicon sprayed into the rubber caps covering the shift linkage. Immediate fix.
Not sure if your s40 has the same linkage, though.