First I have been here long enough to know how to use search  

Recently I started having little issues with the bike:
1. It pops/backfires badly under deceleration (It used to do it before but not as bad)
2. It takes long time to warm up (after 4 miles commute in semi-traffic it still isn't warmed up, approximately 15-20 minutes of riding) It pops weirldy from carbs during warmup
3. When it finally warms up it still pops but otherwise behaves normally
4. It runs absolutely fine when warmed up, no bogging, no hesitation, great throttle response
5. When not fully warmed up it often pops loudly and sometimes dies when I want to take off from intersection after light turned green - this is what bother me most
6. Today it died in a middle of a slow turn... right after I added a little bit of throttle (fortunately I didn't fall)
7. It's hard to adjust the idle because when engine is cold, idle too low, when fully warmed up, idle is too high

My setup is: 2004, K&N Lunchbox, Straight-through pipe (STOCK headers), Jets: 20/65/147.5.

I checked plugs today and they looked fine to me. (I have pictures if you wish to see them)
I played with idle mixture screws today (turned anywhere from 1.5 - 4 turns out) but it didn't help with backfiring/thru-carb popping

I would greatly appreciate any advice on what else I could check. Is my setup too rich, too lean, could there be vacuum leak?
thanks very much!!
KML

my bike pops like crazy under decel as well, well see how this changes with new filter and jets

also takes a long time to warm up, probably around 15 minutes as well to really have the whole engine and carbs warm, probably will get  better with 40 pilots

pops when warm too

although my bike never dies, cold or warm, it does have a strange rattle when its cold, goes away though

adjust the idle when warm, use the choke when its cold

i dont really mind any of the problems though its 21 years old, let it warm up, yours however is considerably younger

check exhaust is all airtight?

Had that issue on a 500 Kawasaki Vulcan and it was the spring in the top of the carb. took the carbs in had em rebuilt and cleaned no more issues and ran beautiful. Wish I still had that bike.

Had that issue on a 500 Kawasaki Vulcan and it was the spring in the top of the carb. took the carbs in had em rebuilt and cleaned no more issues and ran beautiful. Wish I still had that bike.

I will check for tightness of the exhaust.

Today on the way to work it seemed to be almost perfectly fine (Still pops from the exhaust, which is normal to a certain degree). But it died once on me when taking off from intersection.
It seemed to warm up quicker for some reason 

I am lost.
What else, except for the exhaust, can I check?

I will post the pictures of my spark plugs in few minutes.
KML

Pictures of my spark plugs. They are NGK Iridium Spark Plugs.
I will show:
RIGHT CYLINDER: picture 1 and 2
LEFT CYLINDER: picture 3 and 4

each spark plug was photographed from 2 sides

pic1


pic2


pic3


pic4


KML

that being said, i dunno which one that looks like, maybe lean?

which is strange cause your jets seem to be in the right range for your setup

but slow warmup and popping could be attributed to lean condition

try opening the idle mixture a little more maybe that will help

I have seen this document some time ago and according to it my plugs are fine.

Any other opinions?

EDIT: I saw you updated your message.
I too noticed that sparks look to be on the lean side, but I was actually thinking I am too rich... pipe has black deposit inside and my jets are quite large too.

I would like to avoid rejet, but I am thinking of going to 145 main jest and maybe 62.5 mid mains.

I would like to rule out simple problems first, before I spend money on new jets.

I think that at this point it may be important to put a little history of modifications here:

1. at first I had dyno jet kit installed with lunchbox and pipe, it ran fine, but I was afraid that my mixture was too lean.
There were no obvious signs of lean condition though, bike ran just fine.

2. I got rid of DJ kit in favor of original mikuni jets and needles.

3. Bike ran absolutely fine, but would pop under HEAVY deceleration (going downhill on closed throttle = NORMAL for most carburetored vehicles)
Other than popping there were no issues with warm up or anything else.

4. I started putting more miles, as I now commute everyday on a bike and therefore:

5. recently I started having the issues described in 1st post and it feels they are getting worse.

First I noticed excessive popping (even during gentle deceleration), now the warm-up and stalling.

I HAVE to do something about that because it's becoming dangerous to ride my bike  
It died few times in slow traffic on a highway, and yesterday in a middle of a slow turn...

I really need your help here!

My bike also takes a while to warm up even down here in Florida. Gotta get at least 10-15 in before it will not die coming into a stop light. When I try adjusting the idle then it hangs at 4000 all the time. Not sure what to tell ya. Cause now I can't get 'ole boy to start up just the clicking.

Mary

Mary, I replied in your post about clicking. I had this issue when my battery was very weak. Try hooking it to a charger overnight.

Use 2 AMP or 5 AMP settings. No more than that cause you MAY damage your battery.

best of luck

PS. I know that GS takes a long time to warm up, but I never had this issues before, and that's what worries me, plus there are other signs that something is wrong 

Vacuum leak maybe...  When the vacuum cap on my left carb falls off (covers the fuel valve port, since my petcock is manually operated) it pops more and generally runs like crap.

Your experience with the engine dying in a slow turn reminds me of a similar experience caused by the above mentioned vacuum leak combined with a clogged pilot jet. Nearly dumped my butt on Main street.

taking the carbs off and giving them a good looking over can't hurt

check all passageways, needles, floats, jets, screws and places where all the tubes connect (fuel, breather, vacuum, and the little ones by the caps)

^^^
that's exactly what I am going to do. But not today or tomorrow or Friday.
It has to wait until Saturday afternoon.

I wish I could do it now but I got college stuff to take care off.

I will check for vacuum leaks, make sure that all jets clean, check float levels, and if all fails I will reinstall DJ Kit.
If it runs well with DJ Kit it will mean that my fuel/air mixture is too rich on fuel.

other ideas are still welcome!

While the carbs are apart, check the diaphragms carefully for splits/holes.
I would also start the trouble shooting by doing a compression test. If its good, start on the carbs.

how can I do compression test without buying specialized tools?

A friendly mechanic might do it cheap, its a 5 minute job, or you could buy a compression tester, they're not expensive.
http://cgi.ebay.com.au/Petrol-Engine-Compression-Tester-Kit-Set-Automotive-/310249252998?pt=AU_Car_Parts_Accessories&hash=item483c4be886

thanks for link, but honestly why would compression be bad on 6 years old bike that has little over 4000 miles on the clock??

In regards to the pics you posted of your spark plugs; You are running a little rich, see the carbon on the threads? Also looks like the 2nd plug (pics 3+4) is a little richer than the other. But your symptoms are kind of a mixed bag, usually long warm up times are lean, popping usually rich. A balancing seems in order.

Ya the popping and carbon on the plugs say rich at least once its warmed up .... Not having experience with the dyno jet kit have its tough to tell (as I have pretty much always run stock bikes) the long warm up times could be running lean .. or maybe just a clog ... I would defiantly take the advice and pop the carbs, and clean them while i was there, at the worst what could it hurt?