Rex Wolfendon, (T-Rex Racing) Australia's premier CB750 based "Post Classic" race bike builder and racer, builds engines up to 1200CC, using the later DOHC crank and Hi-Vo cam and primary chains, and these weapons produce 140+ BHP at the rear wheel.
He doesn't just build the engine though, he heavily braces the OEM frame, reworks the suspension and adds a very trick box section swingarm, and these bikes are capable of speeds similar to modern racebikes. They are beautifully built, and well known for their quality and reliability. If you want one, pony up the dough, and wait..............
Having said all that, I like Harleys too, and I've no idea why so many here don't? I've owned a stock 1984 Iron Head Sporty and it was a great bike, it didn't leak oil, it was super reliable, and it handled better than any stock CB750 I've ever owned, I raced my buddy on his Moto-Guzzi all the way from Melbourne to Bathurst and back for the last of the Easter bike races in 1987 (a distance of 500 miles each way) and the Sporty surprised us both at how well it performed, and how frugal it was on fuel.
We also had another good friend on a stock CB750K2, who struggled at times to keep up with us. It was definately Moto-Guzzi first, Harley second, and Honda third. Over that 1000 mile weekend ride, we all had the opportunity to swap bikes, but the results didn't change much, my buddy, riding my Sporty got ahead of me on his Guzzi occasionally, but the Honda wasn't able to catch the other two until we got out of the twisty mountain roads and onto some long straights, but as soon as we came up to a corner, the Guzzi and Harley would sail around it.
Eric Buell has just announced that one of the 2007 Buell's, the XBRR will produce in excess of 150BHP, it will be bored and stroked to 1340cc and will feature fuel injection. Nice looking bike, but not really my "cup of tea". Here's a link, and below that, a pic of one of Rex Wolfendon's magnificent race bikes. As I said, I'm a Harley fan, but out of these two, I'd much rather have the Honda! Cheers, Terry.
http://www.diseno-art.com/encyclopedia/vehicles/road/bikes/Buell_XBRR.html