Oooooppppsss! My bad... The cdi I linked is actually for the AC fired stator in the GY 6 engines. Your Kymco has a DC fired stator. I didn't read down the description, and you wouldn't have known to look for that.
I'll go over the options w/ you, and you can decide where to go next.
Option 1: See if the seller will allow you to return/exchange the cdi alone. 3-4 bucks shipping, and done.
Option 2: You can buy an AC stator/rectifiermade for the GY 6 engine, and swap out the stator/rectifier. About 35 bucks but the advantage is your bike will always start, and run with a dead or missing battery. The DC fired CDI's can not start/run a bike w/ no battery.
Option 3: I will buy the AC cdi from you and you can get the proper DC cdi for the bike.
Whichever route you want to take I will work w/ you to get it right.
The 40 MPH is normal for the bike. The next steps to improving that are a performance Var/rollers/contra spring.
After that a larger carb 45 mph
after that a better exhaust 50 MPH
after that a cylinder kit 55+ MPH