Malaguti firefox F15 50cc help!

I have recently finished refurbishing this for my son, it has a previously been deresticted by a previous owner with polini Hi-speed variator, a white (Mallosi?) spring, sports exhaust (make unknown) and a PHVA12 with a 68 main jet. I have fitted new 5.5g roller weights to the variator, It also has a polini filter in the standard airbox
but it only seems to do 30mph flat out. I've tried to find out what the standard jet would be but am unable to find any info.

I was hoping someone could please help and point me in the right direction.

Well...you can check the Spark Plug and the colour will tell you the story if its the right Jet.Original Jet was a 72..if i remember correctly. 30MPH is the topspeed ?Sounds to me their is something restricting your engine .Maybe the CDI

jet 68 is way to small for a derestricted scooter.. try something like 78/80... en also adjust your airintake screw..

Jet for derestricted scoot is 88 and adjust your air intake screw on the carburator

Thanks for the replies I'll put a bigger jet in and see how it goes.