I am 20 years old, a mechanical engineering student at University of Arizona and I work at Spookytooth Tucson, some of the guys on here use these bikes for main transportation, not as toys like us, so they are a little conservative.
If you really just want a nitrous system that works, and is cheap, this is what you need.
Go to a bike shop and get a CO2 tire inflator that takes the little non-threaded cartridges, then go to a smoke shop (some place they sell pipes and stuff) get some 8 gram Nitrous cartridges, 24 pack of ISI cream chargers, Whip-its, something of that nature.
Now the inflator you bought is a little too tall for the nitrous canisters which are shorter than the CO2 canisters, what you do is stack about 5 pennies (yes real pennies like the money, change) So that the needle in the discharger will 'crack' the cartridge.
You now have a nitrous discharger with that handle and its trigger. What I did was use a shcrader valve from an old bike tire, and epoxyd that into a length of fuel line (for one of these engines). The little bit of rubber on the valve from the bike tire helps it hold well stay under pressure so don't worry about getting it scraped off.
Then just run the nitrous line back to your carburetor, position it so that it blows into the airbox. If you have one of the black 4 pipe down filter covers, push the tube into one of the downpipes, if you have one of the slatted round covers just ziptie the pipe into position blowing into the carb.
I use the trigger on the actuator to hang the little discharger from a brakeline while getting up to speed, once you are cruising, just pull the trigger and you will feel a surge of power.
IMO the boost is very controllable and my engine has gone through 20 charges with no problems, ZERO, if it is not actually better for the experience, I feel like it runs a bit more freely after feeling the power.
The sad truth about nitrous is, you do only get a burst of power, and in the end you can't use nitrous to cruise so the point of it is a little lost in the fact that these bikes aren't quarter mile machines.
TOTAL COST $40
24 pack of chargers- $12
Valve, zipties, and glue-$3