I have a common problem with my '97 GS500 (California model) with std air box/filter, 40 pilots, 125 mains. Runs perfectly and makes good power from 2.5K upwards, but once warm, if engine is ever  taken above 2.2K with clutch in, it soars to 3.5/4K as the new "idle" speed. If "forced" below 2.2K, it idles like a dream at 1.6K. Blip the throttle and the idle soars again to 4K.

This is driving a lot of us GS owners nuts!

I've seen this problem posted so many times on the internet but I've seen no consistent solution posted. The 40's had no effect on my idle problem. The idle mix screw has no effect on this problem, at least between 2 and 4.5 turns out, on my bike.  And my choke is fully closeable - and cable is adjusted correctly. I can't find a vacuum problem but wonder why so many people would have the same vacuum line fail? No one suggested which vacuum line is the most likely culprit.

Sorry to say that the suggestions for this VERY SPECIFIC PROBLEM seem to be fairly random. I'm sceptical that it could be  the idle mix screw sometimes, sometimes a vacuum line, sometimes the choke cable, sometimes a choke spring failure, and whatever else I've read here and elsewhere.

Can someone please make an authoritative posting on this problem? Maybe a Suzuki mechanic who has fixed many GS500s? Is it really from such diffent causes? Sorry, but if you've only fixed a single GS it isn't reasonable to assume your single fix is applicable to everyone else.

Thanks

Rich

I'm going to experiment with your bike from here. I hope you don't mind. Adjust the idle to 1.2k. Blip the throttle. What does it read? Ride home (I assume your at work at this time) or take it out for a 5-10 minute ride. Blip the throttle. And what does it read now?

I'm begining to think that the engine is overheating at this higher idle, and when engines overheat, the idle goes way up.

I have the exact same problem. I've been scouring these fourms trying to find an answer. I was going to perform some basic tasks this weekend (check choke, adjust cables, etc.) and then ask for help if it was still happening. The only time I have idle problems it would seem to be heat related (stop and go traffic). I guess the next logical step would be to identify reasons the motor would overheat.

1. poor airflow over the case
2. wrong carb settings (although our engines run fine)
3. wrong heat spark plugs
4. low oil

What else could cause the motor to overheat? My motor was rebuilt 600 miles ago, pulls strong and doesn't smoke.

I appreciate any and all suggestions. This problem is the only thing keeping me from fully enjoying my GS500. Thanks.

Oh yeah, mine is also a 1997 California model. I haven't dug into the carb yet so I don't know the jet situation. I'm assuming they're stock.

Your motor was rebuilt, so it has just finished it's break-in at 600 miles, huh? Right on. Have you done the first service oil change?

Oil change is in the plan for this weekend.

Sweet! Could I ask you to set the idle to 1200 rpm, please?

My idle is set to 1200 +/- 100 RPM.

Richwhiteguy wrote:

QuoteIs it really from such diffent causes?

im afraid so/or it can be i have worked on many gs's, some with the same prob, and a lot of the solutions, some more than 1 of the fixes had to be used to correct the problem. the reason you see so many diverse replies to  the question/problem, is that  1 the reply usually may help, and 2 you are basically throwing out a problem, where no one can actually see/ touch the bike. if there were 1 fix for each problem, it would make my job a lot easier, dont mean to jump you like that i apologise, but like i said these people on this/other boards usually dont have the opportunity to see your bike/its condition. so we have to go with essentially an educated guess. anyhoo good luck to you

I had a similar issue with my bike, the idle would only hang high when the bike was sufficiently warm. Keeping that in mind, I'd suggest setting your idle only when the bike is fully warmed up, maybe even after a full 20 mins of riding. Otherwise if the idle is set when the bike is too cool, it is likely to be set too high.

Good luck!

just to be clear-the hanging idle is a comon condition of STOCK JETTING of the gs carbs. This is caused by a lean air/fuel mixture. RichWhiteGuy has already corrected this carb issue and posted the 40/125 jetting that these bikes should have but still has the hanging idle.

I'm no mechanic but since this condition happens as a result of lean condition then its possible theres still a lean condition (vacuum leak somewhere could cause this).

have you checked the condition of the spark plugs (color that is)?

Thanks for the all the responses. A lot of folks have excellent ideas for fixing the hanging idle, but I still feel that the problem is too specific to have so many possible causes (sorry, but it's my bias as a scientist).

Some things I forgot to mention about my bike specifically:
1 - plugs are both perfect color, with no obvious signs of leanness or overheating. Stock heat range NGKs. Bike gets 45-50 mpg. 13.5K miles on engine. I tried my spare plugs - no change.
2 - the hanging idle begins just after the bike is warm enough to run properly w/o choke (maybe 1 minute at 60 degrees F ambient temp, with the 40 pilots installed).
3 - once the idle starts to "hang", if I force the rpm below 2.2K using e.g. engine breaking and then pull in the clutch, the engine sometimes dies (no idle at all). If I blip the throttle a touch just to keep it from dying, it stays steady at 1.6K unless I bring it above 2.2K, and then it goes start up to 4K. If idle set to e.g. 1.2K, the idle still hangs at 3.5-4K.
4 - the lower I set the idle below 1.6K (I adjust it when hot, like at a stoplight), (I have tried 1.2-1.6K) the greater the tendency to die when declutched at below 2.2K. Fine for me to deal with (lots of experience) but my girlfriend is still learning and having to focus on keeping the engine from dying while braking/downshifting/avoiding zany cagers/etc is exasperating to her.
5 - this summer I didn't have the hanging idle problem! It seems to have developed gradually. At first it was an occasional problem, maybe 1 of ten times the idle would hang, but now it's everytime, and the chance of it dying on declutching seems to be increasing.

I suspect a vacuum line due to gradual development of problem (a growing crack in a hose, etc), but which one??? It seems a bit loony to blindly replace all the lines, but if I was confident that it would help I'd do it immediately. Any suggestions from experience here?

Thanks

Rich

Quote from: richwhiteguyI suspect a vacuum line due to gradual development of problem (a growing crack in a hose, etc), but which one??? It seems a bit loony to blindly replace all the lines, but if I was confident that it would help I'd do it immediately. Any suggestions from experience here?

There is really only one vacuum hose. That is the one that connects the vacuum actuated petcock to the right side of the left carburetor. You need to inspect that hose for the suspected leak. Also, check your intake boots, make sure your carbs are seated properly, make sure the rings on the intake boots are not too tight, as that may constrict the area around the butterfly valve in the carb and restrict it's movement, causing the butterfly to not close completely on its own or hang open. You must inspect all these potential problems to find the actual problem by process of elimination.

Quote from: richwhiteguyI can't find a vacuum problem but wonder why so many people would have the same vacuum line fail? No one suggested which vacuum line is the most likely culprit.

For the sake of discussion, let's just say you have a vaccuum leak.  With this "given" I can think of 3 possibilities:

1) The vacuum line from the back of the ON/RES/PRI petcock to the left carb is loose(1,2) and/or dry(3,4) and/or cracking(5,6) on one or both of the ends, or is cracked along its length(7) somewhere.  However, I think a vacuum leak in this hose would have less to do with leaning out your air/fuel mixture, and more to do with not getting enough fuel to the float bowls in the first place (in the ON and RES positions).  Not my prime suspect.

2) One or both of the "vacuum caps" on the upper right corner of the carbs might be missing(8,9) or loose(10,11) or dried out(12,13) or cracking(14,15).

3) One or both of the tiny O-rings below the just-mentioned caps and the round, black plastic "carb lid" might be missing(16,17) or flattened(18,19) or dried out(20,21) or cracking(22,23).

1 problem (vacuum leak) => 3 suspected areas,  with 23 possible causes.  Still very scientific.

Quote from: richwhiteguy1 - plugs are both perfect color, with no obvious signs of leanness or overheating. Stock heat range NGKs. Bike gets 45-50 mpg. 13.5K miles on engine. I tried my spare plugs - no change.
2 - the hanging idle begins just after the bike is warm enough to run properly w/o choke (maybe 1 minute at 60 degrees F ambient temp, with the 40 pilots installed).
3 - once the idle starts to "hang", if I force the rpm below 2.2K using e.g. engine breaking and then pull in the clutch, the engine sometimes dies (no idle at all). If I blip the throttle a touch just to keep it from dying, it stays steady at 1.6K unless I bring it above 2.2K, and then it goes start up to 4K. If idle set to e.g. 1.2K, the idle still hangs at 3.5-4K.
4 - the lower I set the idle below 1.6K (I adjust it when hot, like at a stoplight), (I have tried 1.2-1.6K) the greater the tendency to die when declutched at below 2.2K. Fine for me to deal with (lots of experience) but my girlfriend is still learning and having to focus on keeping the engine from dying while braking/downshifting/avoiding zany cagers/etc is exasperating to her.
5 - this summer I didn't have the hanging idle problem! It seems to have developed gradually. At first it was an occasional problem, maybe 1 of ten times the idle would hang, but now it's everytime, and the chance of it dying on declutching seems to be increasing.

Now, in reading this again, it's begining to sound like carb synchronization is going out of whack. Especially in point no. 5. You're getting decent caburation as evidenced by the sparkplugs. But one cylinder is working harder than the other.

Kerry, Right on!  What depth! Gives me a new way of looking at a bike! Wow! The details! You're incredible! The time it took to list all that!

The reason there isn't a single answer is cos people omit, mis read, mis describe or over all make in complete observations and post the question. To provide you with 1 solution/cause the basic option is to tell you all the possibilities or keep asking you questions... till finally one possibility alone is left.
So starting with the most likely reason...
1. Does the problem get worse when weather is cold or worse when weather is hot... I mean 90 degree hot (Ok see ya next summer)
2. Vacuum leak check turn up a vacuum leak??
3. Does turning the handle bars left or right make a diff.
4. When you say your choke closes... have you taken the carbs off and made sure they have the internal springs and O-rings in place and intact.
5. What is your float level and have you taken off the mixture screw and checked if it has a notch or a bend in it.
Cool.
Srinath.

I have the same problem on my 2002 it is less than 2 yars old and has about 14,600 miles.  The problem arises in stop & go traffic.  The first time it happened was on my way to the Lincoln Tunnel in the summer time.  I had to lower the screw that adusts the idle. Since that time the idle has been impossible to set correctly if I go into city traffic.  It happens even in cold weather but only when I am in stop & go traffic.  Sometimes it takes me 20 minutes to get into and through the tunnels.
I'm going to take the carbs apart as soon as I get another bike in the spring.  Until than I set the idle low and just live with it.  I have the same aversion to mechanics that I have to doctors.

Quote from: richwhiteguyscratch -For the carb synch, can you recommend a brand of gauge to buy, or should I just take it to the dealer (yuck), and how much should it cost?

There's the PCCC mercury sticks which are pretty popular, plentiful and inexpensive, between $50-60. You may have to order one. If you do get one of these, you will need something like a coat rack to hang it from while you balance the carbs, and use some wire to make loop to hang it with.  I'll see if I can find a link with a picture.

Well, if you go through parts411.com and search part no. 206-511-LP, there's a link to Lockhart-Philips for a picture of their Motion Pro (no longer PCCC) Mercury Carb Tuners w/5mm adapters, but the price is $77!

I found this link though: doh, be right back.

Here it is:

http://www.greenspun.com/bboard/q-and-a-fetch-msg.tcl?msg_id=00BK3k

RE: Carb synch tools

If you're the "roll your own" type, check out the picture and links in the old maintenance thread.