Remove the carb. Remove the float bowl. Remove the fuel jet. Be mindful of fuel in the carb. It does not make for a good cologne.
Also, tighten the jet up with a pair of pliers, both the actual jet and the long nozzle it seats into. I thought I could just do it hand tight, and after only a few meters of running the motor, the jet vibrated loose and fell into the float bowl, where going anything more than 1/2 throttle would make it bog down significantly (it almost literally sounds like the motor is running under water)
Header length (the distance between the jug's exhaust port and the actual expanded part of the exhaust pipe) is what sets where the powerband is. Shape and diameter determine how long or potent the boost is. The SBP pipe is fully tunable, allowing you to get either mid, low, OR high end power, but not all 3 (though I dont doubt it would help all around). The banana pipe because it is not adjustable, only allows high end power (to be honest, the 48cc would see the biggest gains I would think, being at top RPM would set the pressure wave right around the middle) unless you add headers or a custom pipe to set the banana pipe further from the port. There are those with much longer expansion chambers (usually custom made or off of dirt bikes) that get far more power all throughout the powerband than any expansion pipe you can buy for these motors. If you want to learn a LOT about these motors, . If you're new, alot wont make sense to you at first, just work little by little. I found myself saying "THAT's what he was talking about!" alot as I worked on the motor, and I progressed, now alot more of the site makes sense to me.