85SX 2010 Not Changing Gears - Help

[Adrian]

My sons bike is not changing up gears once the bike is at race temp.
Bike has only done 35hrs.
New master cylinder, new clutch kit, top and bottom end rebuild including new crank.

Have found metal shavings (fingernail clipping size) on sump plug.

Have had 3 mechanics take a look at it with no success.

Any help appreciated.

thanks