I won't go as far as to say I don't believe you, HondaMan, but considering that Suzuki isn't getting 150 horsepower out of their '06 GSXR750, I'd be interested in hearing your plan. Even assuming you mean to bore it out to 1000 CC or so, you're still asking 30 year old technology to perform on par with the latest-greatest.
'Splain, Lucy!
Noel:
Action Fours made a drop-in 1000cc kit with crank, rods, cylinders, pistons, the works, in 1974 that we built into an Amen-framed chop, using a K1 engine. Installed a Weber 4-bbl carb and custom intake manifold, CD ignition and distributor that ran off of the camshaft at the tach port. The rear-wheel dyno went 108 HP with just that much mod. Then we did a port job, reshaped the cylinder heads into hemis (see my new post as an example), found some stainless-steel intakes that were 30 degree valves so had to remake the seats. Compression dropped at this point to about 9.2:1 (the stock 1000cc kit is 10.25:1).
We were thinking of a turbo, either one from RC Engineering or Rootes, but the owner ran dry of $$. When we went to the dyno the second time, it broke the chain in 3rd gear at 112 HP, going up. We didn't have another chain, so we lost our final test. My gut feeling was that it went near 120-125 HP then.
Seven years later (1981), I got a letter from the guy when he sold it: wanted the parts list for the next owner's "shop manual". It was still running fine.
I believe some of those kits are still around. With a different cam, more compression and 4 of today's pump-equipped Mikunis, I believe this is a likely 150 HP class engine. But, as we learned from the chain incident, there is a lot more to adding power to a bike than just putting it in the engine. A stock CB would need some serious frame and suspension work, swingarm attention, and some more things to put this power to work without endangering the rider.
It's not a fantasy, nor is it hard to do. Heck, look at Subaru engines today: 305 HP in Boxer engines of a couple of liters. It's about legislation on the crotch rockets: insurance companies limit the HP you will find ever since the Honda Magna killed a lot of people in it's debut year. That HP race with Honda and Kaw caused national legislation to occur, targeting bikes 750cc and up (this was during the early 1980s). You might remember the ill-fated V4 waterbikes that Honda introduced then: they were designed as 900cc bikes that never made it to US shores, because of the new laws. (They became a quickly scaled-down 700 instead, and quite unreliable.) There was a huge "penalty" tariff added to bikes over a certain HP for a given displacement. I haven't heard much about it in recent years, so I don't know the final outcome of that whole mess.
