Had the same problem with my '06, particularly after buying new gloves that were more slippery, so needed to grip tighter. Posted here, I wound some rubber tape round the grip (cut from an inner tube), this helped significantly because I could relax my grip.
I have 2007 fjr ,since March, ....but I can't ride the thing for more then,about an hour, before my right hand goes numb. tried handelbar risers,Crampbuster,did the throttle spring thing,got a throttle lock, even been doing my hand exercises,(spring grip thing) nothing seems to help.So I,am at the end of my rope. Is this a 2007 issue,or a FJR thing? I read Sacromento Mike's yoga riding position, that helped a little but not much, how do you Iron butt guy,s do it?? is the only answer the $1000.00 dollar Aussie McCuise control? How about a ST-1300 have any of you guy's rode them,I would give up the performance ,for longer riding comfort. please give me answers... Larry
Carried this over to my '10, but as more birthdays passed, I was still having a problem particularly on long motorway runs, so I fitted a cruise control (posted here). I've not had a problem since.
Yesterday I did 3 hours much at a steady 70mph (nominal). Easy. Apart from the hail.