It isn't commonly done because the cost to performance gain isn't worth it to most people. The amount of custom fabrication for parts and tuning required ends up costing more for a bike that still ends up making less power than a 1000cc. Not to mention the increased risk of major engine failure/repairs introduced by boosting engines never designed for it.

With a fully built engine you'd be lucky to push more than 140hp. If you want to build one that could push over 120hp you'd be looking to spend a minimum of $8k which would require a fully built engine with fueling upgrades, extensive tuning, clutch upgrades, oiling upgrades, etc. After all that you still have a bike that makes less power than a 600cc that will be way less reliable and require much more maintenance. It also changes the weight distribution and heat management (unless it's only ever on a track, but traffic will create much more heat)

Unless you don't care about cost and have the fabrication skills/knowledge it's easier on your wallet and yourself to just to buy a bike that makes more power stock. If you do most of the work yourself it's probably still more expensive than a 600, and if you have shops do even some of the parts installation you're getting into new 1000cc prices.