Lexmoto 50cc echo plus.. Big Bore Kite, Advice?

I bought my son a new 20 model Lexmoto 50 echo he's done just over 700 miles so it's run in etc. After following him I truly believe it's dangerously slow in every way.
I've taken it to the local dealer to be tuned (derestricted) and unfortunately they say not at lot can be done with it and he will be lucky to get above 40 mph. So i'm considering fitting a 70 or 80cc big bore kit.
Can anyone give us any advice on anything relating to this topic, perils, gains absolutely anything?

Thanks in advance

 

I asume it's efi model ?

 

To be totally honest, I really don't know? lol

 

Does it make a buzzing/wuring sound when you turn ignition on ? Engine management light on dash board ?

 

Yes

 

You may need to contact a main dealer, if it's efi you can't just fit an 80cc barrel as you'll need to increase fueling . Old carb model it's easy !