Wrecked my Seca II 600 last summer, drunk. Lost my license. I'm currently finishing my masterpiece on a 900 frame, naked w/carbon fiber where necessary, +4" modified swingarm, shorter sprockets (should top out 155-164). The original 600 has been bored, stroked, port/polish, jetted, carb has been replaced with high-cfm race setup, 4 to 1 unmuffled, forged internals and running race gas. I have an ethanol kit but not putting it on yet. I also have a small turbo lying around, when I want to go totally nuts my engine and fuel system is ready to bolt it on!!!
I took the bare frame out to the local 1/4 and 1/2 mile backroads, and boy! I was with a gsxr 750, a cbr600rr, a cbr 954, an R6 and an R1. Let me tell you, my seca was a slow-ass commuter bike before, couldn't even pace a newer 600. That day though, I smoked the gsxr, cbr6 AND got the R6 by a couple lengths.... and I was amazed that I could run with the bigger bikes, if not take them in a 1/4. I'm estimating that my bike must now make ~120-130hp to be able to do what it does, close to double the original 70hp!!
When I finish and and detail the frame I'll post a pic, maybe I will have put the turbo on by then..... the shop thinks I can reliably run 160-170hp and ~200!!! If I set up the ethanol! Happy riding!