Welcome to the forum!
We don't get to many s50's through here, but if it's anything like most other newer KYMCO models the CDI may not be restricted in the traditional sense. Most older CDI's are restricted with a rev limiter. It seems in recent years they're not restricted to a certain RPM range, but restricted with ignition timing. I don't know if this is confirmed for sure, it's just a theory at this point. The theory is the CDI retards the ignition timing at high RPMs. Really the only way around this is to purchase a custom cdi or use one from an older model and remove the rev limiter.
Let me tell you my little story. I bought my '10 Peop 50 2t brand new and went at it doing my homework on derestricting it. The three major things I found were the CDI, the variator boss, and a larger main jet. On older models you unplug the green wire with a bullet type connector coming off the CDI. So that's one of the first things I did. Two years later somebody posts something here about how the green wire does nothing. Out of curiosity I plugged the green wire back in. Mind you at this point I have a 70cc BBK and several other performance parts on my scoot. To my surprise I could still reach my top speed of about 55 mph. So all along having the green wire unplugged did nothing. I still don't know what it really does.
Keep in mind Mine is a 2t yours is a 4t, not to mention yours is a year older as well. Yours could very well be completely different.
First things first, what does your cdi look like? Take a pic and post it (don't frustrate yourself trying attach it onto the post
. Use photobucket.com It's free and easy, just copy and paste the image code) Does the CDI have a green wire with bullet connector on it? If so, give it a shot, see if it makes a difference. If not don't get discouraged yet. The CDI may not be the limiting factor (at this point anyway
)
Is the scooter basically stock? If not, what have you done to it?
One trick I learned is a slightly longer belt can get you a few extra mph's.
There is one more restriction that has recently been discovered in these newer models as well. Don't know if you've dug into to the CVT yet, but let me assume you haven't. Basically there is two pulleys and a belt in there. Like a bicycle chain and gears, as you accelerate the belt moves up higher on the front pulley and lower on the rear pulley. That rear pulley has a restriction that doesn't allow the belt to move all the way down to the bottom. Solving the problem? New rear pulley... Should I say an old rear pulley
. Supposedly you can order one for a zx50 and it will work with mine anyway. Not sure about the s50. Now it's not really a problem for me until I get up above 50 mph, so I've just left it alone for the time being. Yours could be different, I don't know. I kinda doubt this is your problem but you should be aware.
You could have a combination of issues or it could be your just not making enough power. They really restricted these newer models. Including tiny main jets and exhaust that isn't worth a sh**. Tuning the CVT with lighter/heavier rollers, stiffer clutch springs and torque spring, and a slightly longer belt is by far the cheapest way to gain speed. Nothing compared to a BBK though. You having the 4t means you're going to struggle to get into our famous 50mph club
. It can be done though. Tell us a little more about what you've already done to the scoot and we'll try to steer you in the right direction.