I regeared my z1k (The engine is a rebored zx9). Went with a -1 front +2 rear. Overall I would say the mod was worthless. The bike doesnt accelerate any faster (also it does feel like it), abit easier to wheelie of the throttle, and top speed was in the 150's.
Higher rev's at highway speed led to more vibes thru the bars, and engine braking was bad enough that I regularly locked my rear tire downshifting agressivly.
I was followed by a friend in a mustang gt, I was going about 40-50 and when it came time to turn I downshifted instead of braking. And damn near got rear ended.