Have you got the original bar ends fitted or some lightweight alloy shite?If its the latter, get the originals back in there. That will reduce bar vibes.
Unbalanced carbs will cause engine vibration which can be felt through the bars.
Quick update on this. Today I went for a 3 hour ride with the narrower handlebars. It was well weird for the first few miles, but after that I was really pleased with them. I feel they are now far better than the full width 758's. More comfy, no problems with turning at all and I felt very comfy and secure, riding around the mid-Lincolnshire twisties.The vibration wasn't bad at all with an empty tank - but as soon as I filled it up it stood out very plainly. The worst was in top, between 53 and 58 mph indicated (bars, pegs, bum - everything vibes). That's the sort of speed we did most of the journey to Stamford and back at, in traffic on the A16 mostly. So no wonder it deadened my arm. Today there were no such issues - in fact no problems at all, with the exception of my old issue of a stiff clutch - so my left inner forearm is aching quite a bit now.Unfortunately, I wasn't able to gather enough reliable info on the vibes, as it was all twisty roads (so loadsa fun!) - just the mid-50's bit is definite. It didn't seem to be connected to a specific rev range, but that speed in top coincides with 3500-4000rpm.I'm considering having my 48/50k service soon, so be interesting to see if that changes anything.REally do recommend the narrower 758's though - makes it feel more like I think it should and less like a Fazer trailie.