I don't have any experience in swapping carbs or racing the machines. No experience in swapping needles or jets to run K&N's or whatever. As far as I am concerned, my bike is antique. While not that old, yet, it's a conversation piece and short trip road bike that everybody seems to like and many identify with. It doesn't do the ring, ding, ding, ding, but has a nice report. It's fun! My 77, in it's original form as to BS38's, stock air cleaners and engine on points, will cold start in one or two kicks and tick over at 800 rpm, no choke. Warmed up about 1100 to 1200. The bike is set up by the book. Timing chain tension, point gap, timing, carb screw settings, all by the book. ( I'm running the pea shooters now, but I didn't have to change one setting) I would say over all, I'm very pleased but not surprised. It's how the thing was designed to work and within published settings or what good would the book be?
I know and do appreciate people that like to push the limits. There are those here with the knowledge and experience that have pushed the limits too far and then backed off to the optimum of what this machine can be. My hats off to them. Without them, we would not have some of the most beautiful and performance minded machines these bikes can be. Without them, we wouldn't have their child's play of knowledge to keep our stock-ish bikes in form and running.
So I think, to anyone new to the XS650 or bikes in general, stick to the stock parts if you can, and get it working well first. You'll gain knowledge and later, be able to make the changes, up dates and to personalize the machine making it "your" bike. I think you'll save money, time and frustration. It's only 1/3 the fun getting there!
2/3 's the fun of, man, enjoying the ride!
(To think, I used to spend all my money on Horses and Whiskey)