I’m new to motorcycles and carburetors in general. I got my 02 ls650 last summer with less than 4K miles on it. Despite the low miles, 20 years is still twenty years and I have begun replacing and changing some things. First off  since there was often a backfire, I decided to overhaul the exhaust by replacing the gasket, pipe and muffler. I used the guide here on swapping out to a hd dyna muffler. This seems to point to needing to size up once or twice on carb jet, at least that what I’ve read. Which brings me to my questions; Where and how do I source the correct jets for my carb? Would there be other carb components that need changed as I size up?  I appreciate any feedback and apologize if this has been covered previously. Thank you

How’s your throttle response? If you are happy with the throttle response leave it alone. Just because you changed the muffler doesn’t mean you HAVE to rejet. There is a chance that in the last 20’years someone else has already done it. You should know what jets are currently installed - and understand why you are making changes - before deciding to make changes.

If you need different jets Lancer sells a nice jet kit with the three most commonly required sizes of pilot jets and main jets, and washers to replace the spacer for the needle. Well worth the price especially if you plan to do more mods later on that will require rejetting.