Join Date: Nov 2009
Location: Lander, Wyoming
I've had a sore RH thumb from ATV & Snowmobile Thumb throttles. And I have rubbed the hide RAW on the 1st thumb joints from not wearing gloves on an aggressive dirt ride or 3. (They were in the Other gear bag.)
I've had sore shoulders, elbows, wrists and left hand (lots of clutch work). But I can't recall ever having only sore thumbs from a motorcycle ride.
Maybe your handlebars are pushed too far forward, causing the grips to point Up a bit. Which could put your entire hand and wrist at an uncomfortable angle? Loosen the rearward clamp bolts 1st, then one forward bolt. Then lightly loosen the 2nd forward bolt, just enough to allow bars to be moved. Tighten in reverse order. (The clamps are stepped, not flat) Re-adjust other controls to match.
Modify at "YOUR OWN RISK"!
Still riding my 1987 KL650-A1. 83,000+ miles & counting