The Blind Man (Bob),
I have a similar model from Northern tools produced by Carter Bros. called the carter Talon. My buggy is about a 2004, not exactly sure, had it for a while. 23 mph is slow for asphalt for that model, but I read you have new tires on it. My model has the stock tires which I would consider pretty fierce as far as mud terrain pattern goes. They are no where close to street slicks, hah. The type of tire you have will affect your speed. Anyway, my carts top speed with stock variator rollers and stock torque spring was about 40 mph on asphalt. As for all your carb issues, you may want to look at ebay, I have purchased several carbs from a dealer for about $35 and it comes with everything even the auto choke (a good buy, and this one has lasted 2 years). Your cart should definitely be going faster, even all stock. Before you attempt to do any upgrades I would suggest making sure everything you have is operating properly. If your vacuum lines are rotten, buy new rubber hose same diam from your local autoparts store. Check your intake manifold, its rubber too (comes off carb), if its rotten buy new one (ill but a parts website in link, make sure you buy the right one. there are two types. less than 10$). Air leaks will result is less performance. Get an iridium spark plug, check to make sure your spark plug wire assembly is also in good shape. If its not, again buy a new one, these parts are fairly inexpensive. I would also suggest checking your petcock and the filter. The whole system is operated on vacuum, so this goes back to if your vacuum lines are rotten and have small invisible leaks you could be loosing performance without visible cause. Check to make sure your gas pedal moves the throttle cable a full open/close on the carb, it will take two people. Just have someone push the pedal down all the way and check to make sure on the carb it opens it completely.
If all that checked out, odds are your problem is somewhat internal. Over time the rollers in your variator get "flat spots" which cause them not to roll as well as they should. Another common thing ive seen is the torque spring in the clutch gets too hot and warps, which can also cause losses (same thing goes with clutch springs x3). You can look up gy6 cvt how it works on youtube and understand completely what I am talking about in 5 minutes. I would suggest doing research on variator weights to choose the right weight based on the performance you want. Same goes with torque spring and clutch springs. If you decide to do this, same yourself a whole lot of time and watch several videos on how to change what I have mentioned. Get the tools you need ahead of time. You will need to buy/piece together/weld your own spanner wrench if you don't have one because you have to prevent the variator & clutch from spinning while you loosen the bolt (or have a really nice torque impact gun). With the tools and the know-how you can do it.
Also it is fairly simple in some models to check your valve clearances, never a bad idea. My cart its a pain in the rear to get to so just something to keep in mind.
Once you've gone through that there is always the electrical part of the cart. You may be familiar with the mechanical form of rev limiter or "governor". These carts have whats called a cdi (ac or dc is something very important to keep in mind). You can get a non rev limit cdi which will allow you to get more performance out of your cart. There are many different companies who make them, but i have had friends purchase the ones on the parts website I will link to you and they had very noticeable gains. Some are very expensive on other websites so I would suggest comparison.
The CVT upgrades and cdi are your best bet to gain performance. cdi installation is two screws and a plug. CVT is a little more involved, but definitely possible. Take the wheel off, and there is like 8 or 10 bolts on the cover and a ground. On that note always disconnect your battery when working on anything of this nature. I would also sugest getting a new gasket as yours is probably shot (in parts link, cheap, make sure you buy the right one). One that's off you are looking at your variator and clutch. Belt has to come off too.
Last, If you decide to upgrade cdi I would definitely upgrade the cvt stuff I have mentioned. Keep in mind your old stock stuff is your weakest link once you start upgrading.
Parts link <<<<<
Good luck,
Matt