Performance - Simply amazing. I'm not sure where to start because there was a smile from start to finish. The power with this much torque so low and hp that never seems to end makes riding a joy. Red line limiter is 6400rpms so bumping the rev limiter isn't very likely. Simply astonishing power whenever and wherever you need it. Shifting becomes a secondary thought because you can grab a handful of throttle from anywhere. If I wanted to rip it at 2500rpms, the bike jumped forward. On the highway, 6th gear, running 75-80 and want to pass NOW?? No problem, just rip the throttle. no need to downshift. The bike explodes forward and you're at triple digits in an instant. (Also worth knowing there is no speed limiter now. No clue what the top speed of this bike is now and I doubt I'll ever experience it!)
In the twisties, higher rpms are a blast. Downshift for a curve and at the apex, rip the throttle and the bike comes tearing out of the curve. No hiccups, blips, burbles or any hesitation whatsoever. The tune was absolutely perfect in every way you can measure a bike. And yet the bike has gentle manners at all speeds and rpms. Just want to poke along? No issue at all. In fact, if it weren't for the CVO 128 derby cover, it would be next to impossible for anyone looking at my bike to know the beast of an engine it has under the tank. Just the way I wanted it.
Fuel mileage - Yep, everything fun in life has a price to pay. In the case of this 128 and its power, the price is fuel economy. Granted I was having a "fun" day with this new throttle but the fuel economy was down around 29mpg measured on the PV. I figure normal riding might be around 32 over the long term and maybe 37 or so for long, cruise-control, highway miles. But anyone interested in this motor should know you will likely be the "shortest" tank in the group you ride with.
Small bit of advice - Please don't take offense if you took a different path with your own engine build, but I really don't "get" the whole small overlap so-called "torque" cams. Ok, I get it if you are trying to save money and are looking for a bolt-in cam, but for only about $500 more for hi-lift valve springs, you can have your cake and eat it too. This Wood 408 Cam delivers as good, if not better, low end torque (with the smaller headpipe and factory heads) then some of the best "Torque" cams PLUS you get all the HP that you would lose with the bolt-in torque cam.
If you're only installing a cam, then a "torque" cam makes good sense. But if you're going to the trouble to pull the heads, cylinders and pistons for a Big Bore upgrade, why leave so much performance on the table by installing a "Torque" cam? The only additional cost for most Big Bore upgrades would be the cost and install of hi-performance hi-lift valve springs to accomodate a higher lift performance cam. Most of the high lift cams require more compression but I'm not sure I see the downside going from 10.75:1 to 11:1 that's in my 128 build.
All in All - For the money, the fun factor in this build is terrific. The bike is very subtle...until its not! Your right hand decides if you just want the bike to be a neighborhood friendly touring bike OR a "let 'er rip" beast. The biggest downside is definitely going to be tires for 2 reasons. 1) rear tires will definitely wear out sooner 2) I won't want to run the tires down as far as I might have with less power.
In summary, this engine build is simply a blast to ride and definitely to be considered if you're contemplating a Big Bore M8 build.