help with Jetting

[1Rrider]

I borrowed a bike for my father to be able to go next week for a ride in Pismo dunes. Unfortunattly the owner has the jetting screwed up. He does not know exactly how to fix it. I am hpoiung you can give me a starting point. It is a KFX400 with a Yoshimura pipe other than that it is stock. Help. I want to show dad a good time.
:confused: