I bought a set from Barnett Clutches. Great quality cables, I went with the stainless steel look. The throttle cables really require no extra length or even rerouting for the Rivcos, and in fact my added inch was a mistake. I had to route them through the left hole by the triple tree for them not to be hitting the windshield. But they work well in this configuration also. You could, at most, add a quarter inch if you really want to get them perfect.
The clutch cable needs something like an inch or inch and a half. Again, it's important to not get too much or else you wind up with it too going way too high before it curves back to the handle. Their clutch cable has a synthetic low-friction lining that makes the action smooth as silk, good stuff.
I'd recommend you take your current ones, measure them, and add 0.25 inches to the throttle cables and 1.5 perhaps on the clutch.
Do not tell them (as they suggest) "stock + 2 inches". Their idea of stock is probably cables for the R3 normal or something, because mine were wildly off the first batch I got. Of course, they did a new batch for free to fix it, but even so, give them very specific measurements of how long you want them, seems safest.
Quality of the cables is excellent. Would recommend.
Barnett Tool & Engineering
