Hello, new member, first post.  I bought a used 2002 LS650 for my son to ride and I've been enjoying it more than he has to be honest.  All stock except I put a foam filter in the air box, installed a raptor petcock and lifted the front of the seat. When we first got the bike, the carb was really polluted.  It had been sitting for at least a couple years and was emerald green inside the carb, everything looked corroded.  I removed the plastic/rubber parts and it cleaned up pretty well by soaking it in some cleaner overnight. Put it all back together and the bike would run, but mid range was surging really bad.  From some of the reading I've done on here that seemed to indicate it was a symptom that may require the white spacer mod.  I figured I'd save the cost of buying the 3 washers and just sanded down the white spacer to an eyeball calibration of about 1/2 original size.  Put the slide back in and now it didn't surge at mid range but I could only get about 45mph out of it on the top end.  Scratched my head a while and decided to splurge for the washers this time and install those instead.  I stuck 3 in there.  Holy cow, what a difference that made!  Bike runs great now.  I don't know if it was just the washers that made the diff or if I had somehow trapped the needle under the holding plate in the bottom of the slide.  I'm kind of leaning that way since I don't remember checking if the needle would move up and down a little bit in the slide against that tiny spring in there when I put the spacer back in but I did check for that when I put the washers in.  Anyway, just thought I'd share in case someone else is going thru this.  Now I'm going to tackle changing the tires, I think they might be the original ones since the bike only has about 4300 on it.  Got tires, tubes and tire irons on order.  Oh yeah, thanks to you all for the tips and tricks on this site.  You wouldn't believe how much they've helped me out with this problem and the other little ones I've run into thus far.

I don't believe it makes any difference if you sand down the spacer or use washers - the engine should run the same if the thickness is identical.

Using washers does allow you to easily add or take away 1 washer for fine tuning.

I think you are dead on GOF, I believe I had trapped the needle under the small plate with the 2 screws at the bottom of the slide.  Only thing that makes sense since I don't think the spacer and/or washer should make a difference if they are roughly the same thickness.  Put a rear tire on the bike today.  I went to a Shinko 140/90-15.  Was expecting it to be a lot worse than it was to get on.  Dish soap spray was the trick, slipped right on with a little nudging here and there.  Front tire will be next as soon as my tube arrives in the mail.