What year is your bike and what handlebars do you have? Mine is a 2012 RGU with TBW. It came with a set of Avon grips when I bought it. When I switched to a set of Wild 1 518's the right side grip was too small a diameter and the throttle hung up. The spring in the TBW was not strong enough to return it to closed. The chrome on the new bars was thicker than the crap on the OEM bars. I tried lubricating it and sanding it but this did not work. We were on a trip so I stopped at a dealer and they gave me a take off OEM grip and it worked fine.
I sent emails to Avon, it took about three tries, I think I finally called them. They had me send them back the one grip and sent me a replacement that works fine. May just be manufacturing tolerances or maybe they had adjusted the internal diameter of the grips as I have heard of others having this problem with non-OEM bars.