So title says it all. I finally tracked down my ignition problem (it was one of the pick ups failing when hot) and during the downtime I rejetted and installed my lunchbox I've had on the shelf for months. Here are my set ups for reference (2001):

Current: Full jardine exhaust, K&N lunchbox, 20/65/145 (two washers and pilot screws out three turns). This set up causes little to no pops on decel but there's noticeable power loss in the mid and possibly top-end as well.

Before (plugs were still showing lean, but perfectly drivable): Full Jardine exhaust, stock airbox/stock filter, 20/62.5/142.5 (no washers, pilot screws in stock setting). This set up caused popping on decel but no real flat spots or power loss. This set up had much more power than my current set up.

I live where it's 820ft above seal level. Should I really still be running lean? I followed the wiki rejet charts and figured this set up should be perfect for my mods. If I'm still running that lean, what jet size should I move up to? Should I also move up the pilot jet size since I'm out 3 turns before the idle would stop hanging?

Is there a quick fix I can to get through the season without having to reinstall my stock airbox? Somehow restrict the lunchbox maybe?

Well as an update, I gave up and reinstalled the stock airbox and filter and the bike now rides and runs like a dream again. Power all across the board and the plugs are back to a nice tan colour after a 20min ride. Seems like I found the sweet spot. My float heights are perfect, fuel flow is perfect, I'm not sure why it ran so lean with the lunchbox when comparing it to other's setups. Still seems like my jet size is way too large for running the stock airbox and stock filter but I don't really care at this point! Bike runs perfect and there's only so much nice weather left in the season for riding.

For anyone using this as reference in the future, here's what I found to work perfect:

2001 GS500. Full jardine exhaust, stock airbox with stock filter. 20 pilot, 65 mid, 145 main, 2 washers under the clip on the needle, pilot screws out 3 full turns, 820ft above sea level.

You're running 20/145 on a bike with just a slip on
If it runs fine, well I guess you be the judge of that, but that setup can almost be run stock - 130 mains.
I run 132.5's in my stock bike with slip on. Its an 95 bike but has 2001/02 carbs and air box + filter in it.
Cool.
Buddha.

Quote from: The Buddha on September 01, 2015, 07:08:36 AM
You're running 20/145 on a bike with just a slip on
If it runs fine, well I guess you be the judge of that, but that setup can almost be run stock - 130 mains.
I run 132.5's in my stock bike with slip on. Its an 95 bike but has 2001/02 carbs and air box + filter in it.
Cool.
Buddha.

Yes I know, but it definitely ran extremely lean with the lunchbox on it. I'm starting to wonder if the bike is running fine with the stock airbox/filter and it's just the ethanol in the fuel causing the plugs to look white. It shows zero signs of running lean. Even in this extremely hot and humid weather we've been having the last couple weeks the bike runs quite cool and the pops and crackles on decel are all but completely eliminated.

I looked back in the records from the previous owner and he does state that he burnt both exhaust valves and did a complete top-end rebuild which included a port and polish and new valves. I did notice some work done on the intake side when I pulled the carbs, but I don't think it was enough to have to run such large jets on my current setup. Oh well, I'm not going to worry about it because it's running fantastic now.

If the flow pattern or compression etc etc has been altered - you can not jet it like a stock bike. Throw away everything I have told you about jetting it. Ignore all the other numbers and advise - nothing applies to you.
Now you may also need to remind me and others in every post you're head has been altered/flowed etc etc. Else we'll tell you advise for a stock bike.

OK here is what you need to know.

If your venturi velocity increases - you need smaller jets.
If it drops you need larger jets.

AKA - simple example. Putting a 40mm carb on a bike with a 36mm carb will have you going to a larger main jet, you will also pull a higher rpm @ WFO, but you may find it near impossible to ride/jet for anything less than 1/4 throttle. AKA - velocity is not enough at small throttle openings to efficiently suck atomized fuel into the air. Hence you get weird lumps of fuel.

Anyway you could be a shade lean, burn white but not be lean enough to notice while riding.
You also should realize - unless you do a high rpm under load @ large throttle opening plug pull (aka ride it in 5th or 6th, @ 3/4 throttle - reach steady RPM/Speed, hold it for 5 sec, then hit the kill switch pull over and check) - you're checking your mixture only @ idle.
So - you could be a shade lean on air screw - You could try a bit more air screw, and fiddle it to the point it starts to run horrible, and back off.

Or it may be the crappie fuel. My favorite excuse when stuff seems to defy the fiddling.

Cool.
Buddha.

I really don't think cleaning up the head will put me in a category outside a normal GS. This isn't a race port and polish with larger valves, I think all that was done was just a little clean up of the casting imperfections by the looks of it. I could just tell someone took a die grinder to it and then polished it up a bit. But without dissembling the head and finding out what was actually done to it, I guess I'll never know. The explanation in his notes was very vague. For all I know he could have shaved the head and upped the compression, who knows.

I'm already 3 turns out on the pilot screws. From what I read you shouldn't go much further out than that. Instead, you should up the pilot jet and start over again with the pilot screw adjustment. Is that accurate? But I'm not willing to rip the bike apart again just to up the pilot jet and start messing with it again. Our riding season here is only so long!

But this is my first time fiddling with carbs. I'm very knowledgable when it comes to tuning FI from scratch, but this is actually my first time taking a carb apart other than on small engines like a lawnmower or my buddy's mini bike.