Do you have pics of the header? I have a muzzy and my old stock one laying around. I can let you know which it is. This will determine what jets to use. And I would suggest KLXsters lidless formula. Works great!

 

Thanks!
I've got it figured out now though, definitely an aftermarket header and I'm guessing a Muzzy one.
I checked out another KLX250s and my header is a lot bigger diameter and no mounting for the heat shield

Cheers

 

Cool good luck. Go lidless! K158 main ,needle washer on top ,#40 pilot and you'll be very happy.