I just got my 1998 GS yesterday.  It has been sitting (winterized) for about 5 years with periodic starting and running.  The guy I bought it from had a mechanic clean the carbs (and unstick a float) about one month ago.  The guy trailered it up to me yesteday about 120 miles.  It starts and seems to idle fine when warm, but when I go to drive it I have some issues.

-Hard to keep it running as soon as I take off and give it gas...it chugs and jerks.
-Once it gets moving there is poor throttle response and almost no power even at WOT.
-When it hits 4200rpm it gets really jerky and I have to hold the throttle wide open for about 10 seconds for it to hit 6000 rpm and then it comes to life and takes off.
-Backfired a couple of times.

I checked the carb bowls by trying to drain them and one of them has nothing in it.  Here is my theory...the jerky ride in the trailer caused sediment to settle in the tank which clogged the carb when I went to ride it the first time.  What do you think?  Is there an easy was to fix this or should I just take it to the shop?  I added a bottle of Gum Out fuel system cleaner to the tank and filled up with premium gas.

Also, is the taillight supposed to be loose to move a little vertically when you jiggle it?

THANKS!!!

You wanted experts ? Oh well, I"ll chime in anyway..

The jostling on the trailer shouldn't hurt anything. You do more jostling just going down the road.

You said one float was dry, I'll bet there is lots of rust in both of the carbs. The drain could just be clogged on one, preventing it from draining.

Are you familiar with the amount of power (45-50hp/30 ftlb) the gs makes ? It's no monster

I'd start with pulling the tank off, checking your daily allotment of rust (there is always some, just how much     ) and then pulling the carbs off and looking for obvious things like a dogs chew toy stuck in a jet.

I'm assuming you've already checked for spark, clean air filter, and torn vacuum boots.

bear with me, I'm new to the GS and fairly new to wrenching on bikes period.  I don't have a manual and I have no idea how to get the tank off, plus it is completely full...is that a problem for getting it off? 

I stuck a small piece of wire into the drain hole on the carb in case it was clogged and nothing came out so I think it is something clogged on the top of the carb.

I had a 79 Yamaha xs400 before this and it was much more powerful than the GS is at this point.  Something is definitely wrong...It takes 10-15 seconds to get from 4000-6000 rpm in first or second gear on a flat road.

I haven't checked for spark, or torn vacuum boots.  I did look at the air filter (from what I could see under the tank with the seat off) and it looked okay...no animals nests or dog food in there.

After rejetting and having numerous problems with my carbs I've become an expert at taking the tank off    Just take the seat off, remove the bolts on each side of the tank where it meets the seat, lift up and down towards the tail a little.  Get a nice long flat head screwdriver and turn the petcock from fuel to off.  The petcock should be underneath the tank on the same side as the frame mounted fuel valve.  Now just disconnect the fuel lines from the frame mounted valve and dump the fuel in the hosesl into a spare container and lift up and the tank should come right off.  Good luck.

-Lucas

Quote from: ohgood on March 31, 2008, 05:16:40 AM
Are you familiar with the amount of power (45-50hp/30 ftlb) the gs makes ? It's no monster

Ummmm, what'd you do to your GS??  most of em put down 35-40hp.
I wouldn't suspect a vacuum issue, if a boot was torn it wouldn't run at high RPM's.  Rip the carbs off and give em a nice thorough scrubbing making sure to clean all the little orifices along the way.  When you're done throw in some fresh spark plugs and see where you're at.  All these things won't hurt anything, just good practice on a 'new' used bike.

Does your fuel line form the petcock to the carbs have a fuel filter?If not add one.A clear plastic one with the gold filtering media works best for me so far.If you do have one check it and make sure it can flow.Also try this  http://www.bbburma.net/FloatHeight.htm and it may help to balance the carbs like this http://cgi.stanford.edu/~sanjayd/gs500/Maintenance/CarbSync or this http://cgi.stanford.edu/~sanjayd/gs500/Maintenance/5CarbSync .If this don't work then I would pull the carbs clean and rejet them.Do you have an aftermarket exhaust or air filter?This will cause a lean condition if the carbs haven't been rejeted.Valves being out of adjustment can also cause some of the same side effects you have.

No on the  aftermarket exhaust or airfilter...it's all stock.  Why do I need to rejet if I'm running a stock bike?

Quote from: Jerka on March 31, 2008, 11:07:08 AM
No on the  aftermarket exhaust or airfilter...it's all stock.  Why do I need to rejet if I'm running a stock bike?

It's not nessasary but it helps with cold starting and throttle response.Shortens warm up times also.

Would I rejet with the same size jets or do I bump them up a little?

Quote from: Jerka on March 31, 2008, 11:21:01 AM
Would I rejet with the same size jets or do I bump them up a little?

I would step up to 40 pilot and 130 main unless you are at sea level.The I'd do a 127.5 main.

Cool.  Where do I even get new jets?  Total noob...sorry.

Quote from: Jerka on March 31, 2008, 11:37:34 AM
Cool.  Where do I even get new jets?  Total noob...sorry.

Seek out the one they call Buddha.He has the jets that you need and can advise on tuning. 

Okay, here is an update...I went out tonight and put about 20 miles on the bike and here is a better description of what is going on now:

-Bogging at takeoff...I have to rev to 3000-4000 rpm and slip the clutch to keep the bike from dying.

-WOT not responsive at 4200-5700 rpm...I can run it wide open in that rpm range at any gear and it jerks and sounds like one cylinder is firing and will not accelerate for crap.

-If I back off the throttle it will accelerate.  Once I get over 6000 rpm it runs great.

-When it is warm it idles fine at 1200rpm, but when it gets hot (at least after 20 minutes of riding) it wants to die at idle.

Any ideas?

I am putting new plugs in tonight...one was totally fouled (the one with no gas in the carb bowl) and one had a very white tip.

It sounds more like the float is sticking and maybe 1 or more of the jets are partially clogged.

Quote from: ben2go on March 31, 2008, 05:40:29 PM
It sounds more like the float is sticking and maybe 1 or more of the jets are partially clogged.

I'm fairly mechanically inclined, but I am scared to death to pull the carbs apart.

Is there anyway to at least try to fix this without pulling the carbs (spraying carb cleaner directly in the carbs)?
Should I wait to put the new spark plugs in?

Thanks.

Quote from: Jerka on March 31, 2008, 05:59:39 PM

Quote from: ben2go on March 31, 2008, 05:40:29 PM
It sounds more like the float is sticking and maybe 1 or more of the jets are partially clogged.

I'm fairly mechanically inclined, but I am scared to death to pull the carbs apart.

Is there anyway to at least try to fix this without pulling the carbs (spraying carb cleaner directly in the carbs)?
Should I wait to put the new spark plugs in?

Thanks.

I would try plugs.Carb cleaners won't do much.The fuel is sucked out of the carb bowls That is where the problem maybe.Pulling the carbs is no big deal.Use a digital camera to take picks of how the cables and hoses are connected.There's only 2 clamps on the air box and 2 on the intake boots.I wouldn't tear the carbs apart.Just remove the bowls(2 screws each) and the plastic floats.Then use parts cleaner in all the little passages.If there's debris or rust in the bowls, then I would consider tearing them apart and cleaning them really good.If this is the case just do one at a time.There's plenty of pics and write ups on this.Check out the Wiki under maintainence.

Okay.  I think I'll try it.  Can I use my spray carb cleaner to clean the insides of the carb bowls or do I need to go get a "parts cleaner"?  Can I take the jets out and clean them and put them back in...should I try sticking a wire through them to unclog them?

Quote from: Jerka on March 31, 2008, 06:34:18 PM
Okay.  I think I'll try it.  Can I use my spray carb cleaner to clean the insides of the carb bowls or do I need to go get a "parts cleaner"?  Can I take the jets out and clean them and put them back in...should I try sticking a wire through them to unclog them?

If your carb cleaner is the high pressure kind it will work.Sure you can pull the jets.They are right there under the carb bowls.I don't think I'd try pushing wire thru the jets they are made of very soft brass and easily get damaged.

Quote from: Jerka on March 31, 2008, 06:34:18 PM
Okay.  I think I'll try it.  Can I use my spray carb cleaner to clean the insides of the carb bowls or do I need to go get a "parts cleaner"?  Can I take the jets out and clean them and put them back in...should I try sticking a wire through them to unclog them?

I'm going to copy-and-paste an extract from some advice (slightly modified for clarity) that I posted to someone else:

Buy the cheapest carb cleaner (fluid, NOT spray) that you can find, and add some (4 to 6 ounces) to the gas every time you park the GS for a while. The idea is to add it to the gas, then ride the motorcycle until the engine is warm (20 to 30 minutes?), then park the thing overnight, or longer. The carb cleaner will mix with the gas and soak the carb jets clean gradually, which should eliminate any problems you might be developing from the long period of non-use.

Do NOT use ANY carb cleaner on rubber parts; it will probably ruin them. You CAN use a silicone lube on rubber, and I've even had good luck soaking stiff old rubber parts in diesel fuel. In fact, diesel fuel is ALSO pretty good at soaking crusty grease off, but do NOT use it on an o-ring chain. The kerosene in the diesel fuel will dissolve the o-ring lubricant which is sealed inside the chain, and the o-rings will deteriorate very quickly after that, destroying the chain.

Many people add carb cleaner before a long ride, ride until they empty the gas tank, and then refill the tank WITHOUT adding more carb cleaner, but that is NOT the correct way to do this.

The carb cleaner works by SOAKING the crud off, so you have to get it into the float bowls and then give the chemicals enough time to work (overnight is good, but 24 hours or more is better). Using only a few ounces at a time is the best way; if you use too much carb cleaner, you can make it MUCH more difficult to start the engine. Moderation in all things... Use a few ounces of carb cleaner in the gas tank each time you fill up until the can is empty, and you shouldn't have any problems with gummy jets... You can also do the same thing if you have to park the GS for an extended period; just keep fresh gas and some carb cleaner in the tank (and float bowls), and at least the carbs (and valves) will be clean if you have to work on them.

Also, adding fuel stabilizer has a similar effect; it keeps the gas usable for an extended period of time. Without stabilizer, the "aromatics" in the gas flash off quickly (evaporate into the atmosphere). Once that happens, the gas is much harder to burn, and it begins to build a gummy residue on everything it touches, especially the tiny little passages through the carb jets.

Some people think that this method is just the lazyman's way to avoid cleaning the carbs, but that isn't really true. If you use this technique but still have problems, you'll have to disassemble the carbs anyway, but the treatment with carb cleaner will help to reduce the crud you have to deal with when you get the carbs apart. Whenever I have to disassemble carbs, I use this method, and when I pull the jets, I soak them in a small amount of the carb cleaner while I work on the carb bodies.

From what you've described, the engine is probably running lean, which will cause it to get hotter than it should. I URGE you to buy a Clymer (or Haynes, or Suzuki) manual for the GS; you've invested a lot of money into your GS, so now you need to invest a little more in order to protect your investment.

Hopefully, that will make sense to you; let us know how things turn out.

Thanks to everyone for the great info.  I will definitely keep you posted and hopefully someday I will be able to help someone out with the same problem.

One more quick question...

Do you think it is safe to drive the bike like it is...I mean safe for the bike (I need to run the carb cleaner through it, right)?  My biggest concern is that I might cause some severe damage.  Is it a big deal that there is only a drop or two of gas in one of the carb bowls and that the same cylinder had a fouled plug?  I've checked the oil level and everything else seems okay...it starts right up and idles great when it's warming up.