A humble appeal for help, to the veterans of this board.

[Funderb]

I will start off my time here on this forum with a forum faux pas.
I need help.

A little about the bike:
It is a gs500, imagine that, of the 1998 persuasion
mods:
-K&N lunchbox
-DJ jet kit for the main
-40 Pilot
-Akrapovic slip on muffler, unbaffled. (off an R1, and surprisingly quiet)
-Drilled out the vacuum petcock, plugged all the vac holes, so now its a normal petcock for normal people.

Heres the problem:

Before the bike sat for only 3 weeks over winter break it was a daily driver, with few problems, other than being afraid of the cold;
on very cold starts, and only cold weather related, white smoke would spew from the pipe.
Massive amounts.
But if it was warm? No smoke. No oil consumption either.
I checked the valves, all within spec according to the suzuki manual i found on line.
Left exhaust valve was a little tighter than the rest, but still in spec.

Now, after the break:
-very easy to start, but erratic idle that requires choke
-dies when the throttle opens, unless you creep it open
-Riding: Very hard to start from a stop, crazy hunting and searching at all rpm
-at low rpm and idle, often the right carb spits out fuel, and will continue to do so even when the carb is soaked in fuel. (backfire, no combustion)
-Compression is good, 145 in both cyl.
(did not do a leakdown test.)
-spark is good and strong on both sides.

I ripped out the carbs, cleaned and resealed everything. There are no vac leaks anywhere that i can find
using your wd40 test.
The left carb slide rest had sheared off where the needle jet holds it into the carb, i replaced that and the orings were still soft and good.

The symptoms are the same, even with new gas, the bike is unridable.

I am stumped, the carbs are clean and good, the float heights are set properly, i am out of ideas, short of tearing the head off and checking everything else.

Any ideas or questions, both are welcome, Ive spent many miles enjoying the hell out of this bike, and i want to keep it going, driving my car around is absolutely miserable.  : (

[adidasguy]

For what its worth, Trey had similar symptoms.
Ended up being a flaky spark plug. Found out when I reversed the plugs - problem went to the other cylinder.
New plugs and all was OK again.
After that, I sync'd the carbs. If you don't have a carb sync tool, try my hillbilly method:
http://gstwins.com/gsboard/index.php?topic=58598.msg665859#msg665859

[Funderb]

With crossed fingers i will do that.
Thanks adidasguy,

As for carb syncing, I actually have used that method before! haha, i was to lazy to buy a manometer, or 20' of fish tank hose.
Thanks for the advice, and i'll be sure to contribute as much as possible to even the balance here on the forum.

[Kijona]

I will start off my time here on this forum with a forum faux pas.
I need help.

A little about the bike:
It is a gs500, imagine that, of the 1998 persuasion
mods:
-K&N lunchbox
-DJ jet kit for the main
-40 Pilot
-Akrapovic slip on muffler, unbaffled. (off an R1, and surprisingly quiet)
-Drilled out the vacuum petcock, plugged all the vac holes, so now its a normal petcock for normal people.

Heres the problem:

Before the bike sat for only 3 weeks over winter break it was a daily driver, with few problems, other than being afraid of the cold;
on very cold starts, and only cold weather related, white smoke would spew from the pipe.
Massive amounts.
But if it was warm? No smoke. No oil consumption either.
I checked the valves, all within spec according to the suzuki manual i found on line.
Left exhaust valve was a little tighter than the rest, but still in spec.

Now, after the break:
-very easy to start, but erratic idle that requires choke
-dies when the throttle opens, unless you creep it open
-Riding: Very hard to start from a stop, crazy hunting and searching at all rpm
-at low rpm and idle, often the right carb spits out fuel, and will continue to do so even when the carb is soaked in fuel. (backfire, no combustion)
-Compression is good, 145 in both cyl.
(did not do a leakdown test.)
-spark is good and strong on both sides.

I ripped out the carbs, cleaned and resealed everything. There are no vac leaks anywhere that i can find
using your wd40 test.
The left carb slide rest had sheared off where the needle jet holds it into the carb, i replaced that and the orings were still soft and good.

The symptoms are the same, even with new gas, the bike is unridable.

I am stumped, the carbs are clean and good, the float heights are set properly, i am out of ideas, short of tearing the head off and checking everything else.

Any ideas or questions, both are welcome, Ive spent many miles enjoying the hell out of this bike, and i want to keep it going, driving my car around is absolutely miserable.  : (

First step, as Adidas suggested, would be to replace the spark plugs. AutoZone carries the exact plug. As far as spewing fuel...that sounds more like one of your o-rings (specifically the ones on the needle seat) has bit the dust. Also, for some reason, your float height might be set too high. Using Ockham's Razor, though, might be best to just try the plugs first.

Now, as far as the white smoke...here's the good news: MORE than likely, it's just steam. When bikes, especially air cooled ones, sit for a while [especially in cold weather] condensation builds up in the engine (crankcase included - that is, within the oil). Don't worry though! The water will naturally evaporate as the engine heats up. The problem, though, is that if the engine isn't allowed enough time to run to do the aforementioned, water will build up in the oil. You'll notice it when you change the oil - it will look "milky" (my father had an old Moto Guzzi that suffered from the same problem - he ended up covering parts of the cooling heads with leather during the winter). It's really small potatoes, though. Don't fret over it.

The second place water builds up is within the exhaust. The fact that you're saying that it only does it when it's cold is indicative of it just being steam. With GS500's...there's only three things that will make it smoke: water, fuel, and oil. Oil smoke is blue, water is white, and fuel is black. If it was a water cooled bike I'd be telling you to inspect your head gasket. Since it's not...I won't!

Another thing to be sure of is that you replaced the float bowl gaskets. If you're seeing fuel on the carbs...more than likely that's where it's coming from. A less likely source is the drain screw. Did you replace your float bowl screws with cap bolts?

Edit:

Also be sure that fuel isn't trickling down the main line from the petcock. It's possible your mod may have started leaking. Just being thorough!

[adidasguy]

You can use 50  cents of clear, 1/8" tube and check the float levels to be sure they're OK.
Connect a hose to each carb drain. Stick them up high then open the drains. The fuel will raise to the level in the tubes.
If one way off, then adjust float and float needle on that carb. Level should be about mid-way of the gasket line of the float bowls.

[beRto]

What do the plugs looks like? (Do you have a photo?)

With GS500's...there's only three things that will make it smoke: water, fuel, and oil. Oil smoke is blue, water is white, and fuel is black.

A lean engine (e.g. vacuum leak) will also generate white smoke. Although the smoke probably would not be intermittent if that were the problem here.

Maybe I misunderstood, but I read the white smoke was observed in cold weather (not after extended sitting), so I'm not sure this problem would represent moisture build up either.

Perhaps there is a loose fitting that is pulling away when cold (thermal expansion)?

What do you mean by "massive" amounts of smoke? It's really unusual to go from no smoke to massive, with no change other than weather.

[SS Adrenaline]

I had a similar problem with my cb450s and all I had to do was change the plugs.  Works great now.  I did learn to turn the fuel valve to the off just so there isnt any fuel leaking into the cylinders when the bike is using its side stand.  The Gs has a different valve though so that shouldnt be a problem.  Good luck. 
P.S Both of my bikes have white smoke too when its cold.  Its just the nature of the beast and will go away when warm.

[Funderb]

It was the easiest solution, the plug on the spitty cylinder was bad. And it was only 3mo old. dang.

I reset the float levels using calipers leftover from my engineering days, and they were indeed high.
The thing runs like a champ now, probably thanks to cleaning the carbs 3435352 times.

Still, it is smoky or steamy in cold weather, its hard to tell which. But it is exactly this:
All starts represent an engine that has cooled to ambient, or close to ambient temps.
I'd say its mostly after sitting overnight, but that is usually when i start the bike up!
Warm weather startup, no white stuff
Cool weather start, a little smoke, maybe 2 seconds (50-60degf)
COLD (30-40 degf) plumes of white junk, like the bug truck, if you are familiar with such a thing.
This is florida, it doesnt get much colder than that...

I was also thinking - Valve seals, a little oil goes a long way, and if they leak when cold, its possible. But there is no oil fouling to see, so Im stumped.
(I could always Youtube a video, if anyone is interested in witnessing the epic smoke screen.
I wont disgrace you with pics yet until she gets a new coat on. )

I have resealed and reoringed all the fittings under vac so maybe if it indeed a vac leak, it will help.

and clarification on the spewing fuel, i used my words poorly, it spewed fuel/air mixture back from the throttle area, without lifting the slide... It has done that from time to time when the bike was cold, and i was cruising around slowly at 2k rpm or so.

I am glad to have her back, thanks to you guys and all your help, and believe me, i am thankful.
The not of this bike, especially with the akro exhaust, is one I am glad to hear again.

[Kijona]

What do the plugs looks like? (Do you have a photo?)

With GS500's...there's only three things that will make it smoke: water, fuel, and oil. Oil smoke is blue, water is white, and fuel is black.

A lean engine (e.g. vacuum leak) will also generate white smoke. Although the smoke probably would not be intermittent if that were the problem here.

Maybe I misunderstood, but I read the white smoke was observed in cold weather (not after extended sitting), so I'm not sure this problem would represent moisture build up either.

Perhaps there is a loose fitting that is pulling away when cold (thermal expansion)?

What do you mean by "massive" amounts of smoke? It's really unusual to go from no smoke to massive, with no change other than weather.

Well, yes and no. My 98(97) has a pretty bad vacuum leak and I've yet to see it smoke at all. I guess it's possible if the plugs were REALLY bad, the fuel could be coming out unburnt but it seems like it wouldn't even run if it was that bad.

[Kijona]

It was the easiest solution, the plug on the spitty cylinder was bad. And it was only 3mo old. dang.

I reset the float levels using calipers leftover from my engineering days, and they were indeed high.
The thing runs like a champ now, probably thanks to cleaning the carbs 3435352 times.

Still, it is smoky or steamy in cold weather, its hard to tell which. But it is exactly this:
All starts represent an engine that has cooled to ambient, or close to ambient temps.
I'd say its mostly after sitting overnight, but that is usually when i start the bike up!
Warm weather startup, no white stuff
Cool weather start, a little smoke, maybe 2 seconds (50-60degf)
COLD (30-40 degf) plumes of white junk, like the bug truck, if you are familiar with such a thing.
This is florida, it doesnt get much colder than that...

I was also thinking - Valve seals, a little oil goes a long way, and if they leak when cold, its possible. But there is no oil fouling to see, so Im stumped.
(I could always Youtube a video, if anyone is interested in witnessing the epic smoke screen.
I wont disgrace you with pics yet until she gets a new coat on. )

I have resealed and reoringed all the fittings under vac so maybe if it indeed a vac leak, it will help.

and clarification on the spewing fuel, i used my words poorly, it spewed fuel/air mixture back from the throttle area, without lifting the slide... It has done that from time to time when the bike was cold, and i was cruising around slowly at 2k rpm or so.

I am glad to have her back, thanks to you guys and all your help, and believe me, i am thankful.
The not of this bike, especially with the akro exhaust, is one I am glad to hear again.

Oh jeeze...THAT much smoke?? I think a video would be helpful at this point. If it was steam it would dissipate quickly. If you're saying it's generating a cloud of smoke there's obviously something going on. I had a KLR650 that had worn out valve seals and if you let it sit overnight after riding it, it would puke lots of blue smoke for about 5 minutes and then quit after it warmed up. Try putting your hand in front of the exhaust and see if you feel any moisture coming out - on my KLR it was so bad that it would spit oil all over your hand. Funny enough, oil consumption was only about 300mL every tank or so, and it had a 7 gallon tank.

What's stumping me is the fact that you're saying it's white smoke. I guess it's possible the fuel is sitting in the cylinder after running. Just seems so unlikely that it would continue to run if the carbs were leaking that bad.

[sledge]

Cold engine?......white smoke for a few seconds?.......Totaly normal 

When the ambient is very cold just about all I/C engines will produce some `white smoke` on startup. Why?.....Because exhaust gasses cool down when they hit the cold pipework and any contained and now cooled water droplets instantly freeze when they hit the very cold outside air, this produces visible ice crystals which look like........you guessed it...white smoke.