There's a lot more than "fine tuning" called for here. The #250 main is a long way from what even a performance modified 750 big bore motor can handle, and the 27.5 pilot is marginally too rich; at sea level to 800' 22.5 to 25 is what usually works. The needle is the generic 6DH4. Some folks have luck with that, but most of us find that the 6F9 is easier to work with. If the generic Q2 needle jets are in there the buyer would be looking at replacing every piece of brass except the slides to baseline those carburetors for the XS650.