I've had problems with discoloration when using the Pin-Sol method however I found if I follow up with a little soda blasting things really start looking nice. SB is cheap, EZ but a bit messy. Also, due to the wear and tear over 30+ years of use I often opt out for a new carb with nice fresh jets/slides/needles. Kevin, you might want to get a 3.5 slide to play with at some time too. Another option is using a good proven carb (a good thing instead of dealing with a mystery carb). Remember these bikes were originally designed to run on Yamalube R @ 32:1 but Yamaha also recommended Shell Super M or Castrol R30 mixed @ 20:1. Oils have advanced 10 fold over the years and who still uses those ratios? These are a few pieces of the puzzle to consider when getting ready to jet/tune. Your approach to jetting/tuning the bike can vary but some guidelines when tuning the motor are:
GOOD, fresh high octane fuel and oil
Decide on what oil/fuel ratio to use (probably what you want to race with)
Plenty of time (you don't want to rush this process)
One change at a time (don't change the PJ & MJ at the same time)!
A logical sequence of test events (Don't jump back and forth between jetting and timing changes)
A good, safe test area that offers hard packed dirt and deep loam (helps load the motor)
Many, many new spark plugs
Doesn't hurt to have a knowledgeable friend help around to lend a hand & tell you how they see the bike running. I also like to have some compressed air handy to blow any dirt/dust off the carb before disassembly. A 2 stroke tuning book to helps you keep your mind straight during the process too. YZ 465/490s are known for problems in tuning so don't make it any harder on yourself than you have too. If you have all the pieces in place tuning the motor can be a lot of fun instead of a frustrating ordeal. Do what you can to make it fun.