Kelvin, the main jet i guess you're talking about, the size you already have in the bike will be the most efficient in terms of correct fuel mixture at higher revs for max top speed.
perry
October 2013
I can answer this question...
what is the best size jet size to improve speed for s piaggio zip 4 stroke ?
howtomendit.com for free repair help, information and advice.
Try fixfault.com to fix motorcycles.