okay dont post much but read alot on here, I am a streetbike dragracer, and have my old 87 banshee for the trails. I have a 05 GSXR1000, the motor is fully capable of getting in the upper 9s stock, problem with the liter bikes is weight and wheelbase launching. Lower and stretch them and there ya go. Or put it in a banshee chassis set up right and no problem running 9's though some nitrous or turbo on there and 8s are easy. I have a turbo on it now and dyno about 230 and run 8.8s all day. 100 percent stock engine/clutch. And I weigh 220. I was running high 9s on stock motor. Weight makes a huge difference with these light weight bikes.
If I wanted to make a drag banshee it would prolly be a turbo GSXR 1000 motor in it, or at least a 60 hp dry shot. either way you looking at about 210-230 hp plenty to get low 9's
And as was said, alot of guys just cant launch I remember when I had my 00 busa stock pipes just lowered and geared running 9.8's, most guys running low 10s wondered what I did to it. The rider makes a huge difference. One guy can get on a bike run a 9.50 another guy same weight cant get into the 9's. Launching with alot of power in a bike is harder than people realize.