That cvt sucks. Although it's the easiest way to get your bike running, you'll find soon that you seek something leaner and smoother. Eats power with a fresh belt peak efficiency of 95% and only gets much worse, too much engine braking, smokes belts on hill climbs, difficult to change driven unit springs, weighs approx 20lbs and if you fail to tighten a part down and it blows up you'll never find the pieces. Go with a single speed, gear it approx 7.3:1 and use a $30 max torque clutch with a spring rated for 3100rpm or so (agk). Use whatever chain your sprocket is for. You can use #41 on sprockets as thin as 1/8" but it will wear the chain faster. My sprocket is .156" so there is .093 wiggle room but it doesn't bother me. As for a jackshaft I think agk sells a single speed jackshaft kit. This is the best option in my opinion and you will save at least 10lbs and have only clutch shoes to replace at $12 for a set, probably once in 2000 miles.
I disagree. That cvt clearly eats up a ton of your power, my bike does the same 48mph with significantly less power but a 2-speed twin clutch/twin js 4-chain trans. 150cc Briggs FLATHEAD with awful compression and flow in comparison to ohv and only mod a .030 shaved head. two days ago I hand ground my own performance cam (plastic Briggs cam filed down base circle) and advanced timing. Now although it won't rev any more than the springs allow the butt dyno tells me I can go back up to a 7.6:1 from my current gearing of 8.15:1.
2nd thing, that whole thing about not using an mt for over 30 is complete BS. Assuming a 26" wheel with 7.7:1 ratio which is 100rpm per mph, yes it's true, a stock clutch geared for 50 at 5k will burn because it is locking far too early. A clutch needs to slip smoothly with a reasonable lockup speed. A heavy spring will fix this; i.e. Full lockup of 35ish instead of stock 20ish. FYI I put over 1500mi on my single speed setup with 8:1 ratio like this all on the same shoes and spring.
3rd, the price of the mount and JS is reasonable in my opinion. It took me 30mins to make my aluminum mount blocks on a Bridgeport. Ghettos mounts have built in sealed bearings apparently which require precision boring in the metal, overall probably takes 2-4 hrs of small quantity production work for one set. Typical machine shop rates are around $100/hr, maybe more or less. For the price of the ghetto setup you could have bought a flux mig welder and Bmi hangers and done it yourself but it would take a few hours to do the welding, prep, etc, not to mention all your mistakes like burning through the frame as a newbie. depends on what you bill yourself at. $25 an hour? It's the same price or cheaper. $50 an hour? Save time and hassle for a day of your work.
4th, nobody runs bone stock motors off the shelf. A 212 with a normal air filter, header pipe, governor delete and rejet carb will make an easy 9hp. 6hp is at its governed speed of 3300 or so...
5th, The smart choice is to "work smart" and make the money doing what you get paid highest to do best and pay somebody else who has done a few of these to setup or fabricate your transmission (or buy a ready made jackshaft). Or you'll end up like me, working on this extremely difficult project for a dollar an hour. My project? First bike- Hours? No idea. Hundreds of hours. Including Internet research. Total cost billed at $25 an hour? over 10k... Of course my next bike will cost me around $1200 parts and maybe 50hrs of work..
Go to agk, get their jackshaft kit, get a max torque clutch and buy the green spring? Buy a few, 2800, 3100, 3300 and also buy 6 heavy shoes. Running an even heavier spring with heavy shoes will further smooth out the lockup.
FYI the power of the 212 will eat regular bicycle components. You must upgrade everything and start with a very strong frame such as a felt. I've had two frame cracks on my bike both in the rear... The second one I was going about 40 and I felt it right away was very scary.....