I have filed & sanded down the bars twice now to 22mm. Doesn't need to be precise. Generally the bars I use (Protaper & Sunline) are knurled on the clutch side (& fatter), & smooth on the right. Be careful not to use any force sliding on the clutch perch, as this fractures easily. I've found that the right (throttle) side needs no work.
I've got fat bars on Rox Risers on Gus. They taper down to normal sizing anyway. I crashed fairly heavily last week, & they stood up to that well.
My '91 R100GS thread is here
My Ride photos are here
It's just better when there's twins involved....
Box'a'bits screwed with this post 12-04-2012 at 06:16 PM