30-40mph???

The squish band is a cut in the combustion chamber that's at the same angle as the crown of the piston, how it works basically is you set up your engine so there's very little clearance between the piston crown and this "band" cut in the combustion chamber, typically a good squish clearance is 0.25mm up to about 1mm and it loses its effect quickly if the clearance is more than about 1mm. Basically what this does is keep the combustion and flame front at the center of the piston crown keeping it away from the edges of the crown where detonation can occur. Having a tight squish band basically let's you get away with considerably more compression before the threat of detonation becomes a problem. Other benefits are the ability to run lower octane fuels, more timing advance, and more compression without the worry of detonation. There are still limits tho and the tighter the squish clearance the more effective it becomes.
You can set it too tight and the piston may hit the head after the engine warms up or if a bearing gives out (this will cause more problems than just the piston hitting the head tho if a bearing goes at high rpm), and it can still detonate if the compression is too high, octane is too low, or too much timing advance is set, but this does let you get away with more so it's possible to exploit this in order to make more power.
not all engines will benefit from a squish band and it does depend on how the engine is set up to some extent, but for the most part, a squish band can be a good thing on these little engines.
This is why some builders are against ramping pistons since it also gives a passage for the flame front to the edge of the piston where detonation occurs. You can get away with some ramping with a squish band but not much, typically keeping the ramps depth 1mm or less won't disrupt a squish band too badly on a street engine with moderate compression, but on a race engine that depends on a tight squish clearance it could completely negate the benefits of having a squish band when all the engines tolerances are right on the edge for max performance. That's why you may have seen some of my earlier posts mention to ramp a piston to see how another mm would effect the performance, then cut that amount off the exhaust roof and replace the ramped piston with one that's un cut, this is to preserve the squish band and compression ratio for max performance. Basically you cut the piston to experiment, then cut the port when it works and put the un cut piston in once you get the porting dialed in... this is for max performance or race engines, ramped pistons can stay in on lower performance engines to give them more power or port duration, but won't bring home any wins at the track, but it will offer a street engine some nice performance gains without having to cut on the cylinder.

Thanks for all the detailed replies!! This is all very helpful!! Today, I took my bottle boost off my bike, I put a stock intake on in it's place. I haven't tried porting anything yet but I wanted to know if I could reduce 4 stroking any by removing it. I was happy that it did seem to reduce it a little bit. It still 4 strokes when I first start it but after it warms up it becomes very minimal and there is none at WOT. I'm using Opti-2 at 100x1. I didn't gain or lose any power but the motor actually seems to be running better by removing the bottle boost. The intake looks perfectly round and I was wondering if it smart to port the intake any? Also, I've decided to get a Fred Head or other high compression head. If I do this, do I need to get a shorter jug to minimize squish to notice any increase in performance? Oh, one more thing, when I was riding I tried to duck down into a kinda tuck position with my head down a little bit and I topped out at 31mph. I was kinda surprised that reducing the wind resistance just that little bit made a 2mph difference.

Yup... the blowback is normal and porting the intake side of the piston or lowering the intake floor will cause a little more blowback, I just clean my air filter a little more often but the blowback also keeps it clean as far as dust and dirt sticking to its concerned. A reed valve would stop the blowback, but we would have to do some more porting and piston prep to be able to take full advantage...

Hopefully you're enjoying the new found power and the vibration and such will go away or at least a lot of it will go away as the engine breaks in. The 40T sprocket will also help by putting slightly more load on the engine and reducing cruise rpm, and the sbp pipe will give you even more torque and power, which will more than make up for any loss of acceleration by installing the 40T sprocket. Just run it and let it break in good and that'll let the engine make more power as well as run smoother and you should hit your speed goal by the time it's broken in if not before. Just don't try to tune your carb until after the engine breaks in, it needs to run richer to keep it cool and add extra lube to everything. The engine can run pretty hot before it's broken in so keep the first several trips short and close to home.

I'd check the carb and intake, make sure you didn't knock anything loose, or crack anything that'd cause an air leak.

Good to hear it was just an intake leak... I'd just keep it slightly on the rich side while it's breaking in to prevent it from overheating too badly.. as you have seen, these things get HOT when breaking in. When I break one in I just start it up and let it run for a few minutes, set the idle and then shut it down and let it cool all the way, then after it's cooled down I ride it like I stole it but shut down as soon as it starts to show signs of getting hot, usually within about 5 minutes of full throttle accelerations and slow downs it'll be quite hot. Let it cool and repeat but after about 3 or 4 of these 5 minute floggings it should be loose enough to run it longer. It's those full throttle acceleration runs that load up the rings and helps them seat really well, it's gonna get really hot doing this tho so keep the trips short at first.

That's a good distance for break in purposes as it doesn't have a lot of time to get too hot, even tho you could still overheat one in this distance. It can still overheat in this distance but keeping the trips short will keep the odds in your favor. Once the rings start to seat you'll start to notice the engine start to get smoother and more powerful, if you're not already noticing this. Your top speed can also go up quite a bit as it finishes breaking in. You should be noticing some of this by now but it can take 2 or 3 more tanks before it's completely broken in.
Just keep doing what you're doing and maybe start monitoring your top speed if you got a gps app for your phone that will record your highest speed reached. Just don't stay up there very long, maybe go for it then back off to cruise speed or back to varying the speed.

Have you seen this site? There's some good info there. Since you have a 66cc engine, I'd try balancing the rotating assembly.

http://juicemotoparts.com/high-performance.html

"Supposedly" the engine was designed to be a 48cc, but china started slapping on bigger jugs and pistons, throwing the balance off. Not sure how true that is, but I will say that my 48cc engine sure is smooth.

The X chamber is going to give you more torque and more power at rpm... usually a dirt bike x chamber will give you a nice fat power band and the good ones to use are the KX65, KX80, CR80, YZ80 or RM80 pipes, these are all fairly similar and easy to mod to fit the bike. I used a KX65 pipe on my last build and got an adapter from Fred's website that helped speed up the process and I'm very happy with the fit and ease of installation, just had to re clock one bend and weld the pipe to the adapter and done, andd best of all, it's a slip fit with O rings and it uses springs to hold the pipe onto the adapter.
Personally I would go with the pipe before changine sprockets, even tho sprockets are cheap and easy to swap out, but the pipe is going to give you a lot more power and a good amount of usable rpm up top so you will gain more top speed there as well... like 3 to 5mph if using a dirt bike pipe. The sprockets are going to gain you about 2 to 3mph by switching to a 40T and about 5 mph or so with a 36T. Personally I like the 44 or the 40 since my bike exceeds 40mph with the 44 so I still have excellent acceleration and hill climbing power.
You could switch sprockets and trade some acceleration for top speed, then get the acceleration back when you put the pipe on but it depends mostly on what you want it to do, if you don't mind losing some acceleration and don't have any hills to deal with, the sprocket swap is a good way to get more speed, but if you got hills to deal with or really like the acceleration, get the pipe first.

That's a nice looking bike and I saw the other pics you posted with the bags mounted, they do look like they were made for that bike and I'm sure it makes it a lot easier to carry stuff too.

Yeah, if your not looking for speed in particular, the yz pipe will still help the bikes overall performance and hill climb since it'll enhance the power thru a wide rpm range.
For the sprocket, if you're trying to eliminate the rag joint and put in an adapter I don't blame you, I put an adapter on the stingray and it's a lot better setup. It looks way better, it doesn't damage the spokes, and it makes swapping sprockets a breeze. Another really good benefit from the adapter is that you can adjust the chain alignment if it's not perfect. I want to put adapters on my other bikes but the fixie hub doesn't go straight across so I did something different on that one so it don't use a rag joint and for the mountain bike I've been thinking about converting it to a single speed and getting rid of the derailleur then just running a single smaller sprocket off the pedal cranks and a slightly larger rear sprocket so it'll be easy to pedal since it runs off the engine 99% of the time, about the only pedaling I do is to get around in the parking lots and I use the engine for everything else, pretty much the only reason I'm keeping pedals functional is to keep them considered bicycles...