if this is anything like the WRs anmd YZs , they came with a 12mm pin and i think they were dropped to 9mm. you can go into TT and do a search there.
i simply took mine out completely without even thinking about it. figured the slide would hit the cap when i was WOT.
later i checked it. made me laugh. everyone had gone out and bought the 9mm stop. i measured the gap without the stop and it was 8.5mm. so for a few quid they'd stopped the slide 0.5mm before me. arf! arf! arf!
you won't have to rejet.
as sacberg says, take off the black plastic throttle assembly protector, look at the rotating barrell and spot the little, little knob of alloy at the back.
regards
Taffy
Taffy