Been traveling over the past week...and falling a bit behind here.
I pretty much agree with eveything in the past three posts. In the end, it boils down to what you consider a worthwhile project. There are lots of ways to get 110cc+ and 60mph power has never been easier. At one time, the scene was very different...60mph was quite an accomplishment and 99.9% of the parts could only be imported as the US side of things lagged way behind Japan & the EU. Things have more, or less, gone full circle. IMO, the US scene is now the most dynamic and, since the greenback has regained some ground, JDM parts are the most affordable they've been in over a decade.
OTOH, it is well beyond a decade later, there's now a lot of experience behind us and a lot of changes. The one constant: no matter what one decides, there will always be at least one significant compromise. Jarred & I have discussed various concepts as to what constitutes the ideal bike...and reached the conclusion that there is no such thing. At a minimum, a hardcore enthusiast who wants it all will need to build at least 2, or 3, very different bikes.
My view, FWIW, is that the more years & miles are in your plans, the closer to stock your setup will be...albeit fortified in some way(s). I've really learned to appreciate the kind of balance that's possible with an OEM development team & budget. There have been a lot of lessons learned the hard way. Since this thread has focused on building a rock-solid dual-sport machine, with real road capabilities (offroad, you'll never be able to use 60mph power) I suggest that you keep sight of the big picture. Horsepower, displacement and purchase price grab most of the attention but, they're just headline numbers and say diddly-squat about the riding experience you have in store, from the saddle, where it counts. The basic design and layout of the CT70 can't really be changed very much, if you wish to retain all of the versatility of the original bike. Retaining (hopefully improving) balance (stability, suspension capability, braking) takes real planning, effort & bucks. The faster you want to go, the more rolling chassis upgrades will be needed to deal with the added stresses. Most guys are seriously averse to the costs of the upgrades needed to balance a big infusion of power. If this is going to be "meat & potatoes" rider, you'll want to stay on the conservative side. If, otoh, it's going to be a permanent project, or other type of limited-use machine, the less breakdowns/parts setbacks will matter and the further you can push the limits. An ATC110, 125m, CT110, or similar, lump can fit the bill. They'll all be durable and deliver about the same torque, regardless of the hp differences, meaning roughly the same usable speed range. For that matter, an extra 30lbs in the boiler room should actually improve straight-line stability. It's what you want and are willing to do to get it. IMO, most guys overestimate how fast they'll actually ride, over any distance; that's a common mistake that can result in a lot of wasted effort(s).
As you said, lots to consider and probably best approached from a longterm standpoint.
