Hello,

I'm Newb McClure! You may remember me from other posts like http://gstwins.com/gsboard/index.php?topic=61483.msg712742#msg712742 (Problems with my GS500E running)

Well, I've finally figured out what's going on after riding it a whole bunch.

I think it's all in the throttle cable. After it warms up, it idles normally. As i ride it and accelerate, something causes it to stay idling at 3K RPM or higher.

If i'm stationary, and turn the handle bars left or right, it revs even higher. It seems like something is pulling the throttle cable and not letting go maybe?

I know this sounds like a silly problem to describe but that's the only way i can describe it. If i turn it off and let it sit a bit, it idles normal again until i ride it around and accelerate.

Interestingly, it only idles that high when the clutch is engaged or it's in neutral. When i try to go into first and move, the engine quiets up a bit and dips to about 1500 or so before it takes off.

while riding, it seems ok. Any ideas on what I should look at in further detail to get this issue resolved?

i'm sure i'm missing other bits of important information for you gurus out there. Please let me know what it is and i'll get right back as soon as i get home tomorrow.

Also, I'll try to post a video when it's happening so that you can see it first hand.

Thanks again all. Appreciate all the help and advice thus far from you guys.

Anoop

2000 GS500E aka Matilda.

could also be sticky choke cable if its affected by moving the bars

Check the choke cable as this happened to me. The choke cable would open the choke and but wouldn't allow it to close causing my idle to be very high no matter what, around 4k. Since the choke was on all the time without my knowing.

I figured this out when I took my tank off to clean the air filter one day and noticed that this little bar on the carbs (part #59) here.
http://wiki.gstwins.com/index.php?n=Main.Carbs
Was moved over and the choke cable was not allowing it to spring back to its normal state. So I had to push it back over with my fingers, haven't had time to replace/fix the cable yet but now I know what the problem is.

I'm not sure if its the same on yours since it's a bit newer than mine, but if so try it out.

I've heard this from other sources as well. I've also heard that the throttle cable may be having issues.

I'm planning to replace them both if they're easy enough to replace.

Interestingly, this condition where it revs really high doesn't happen until after i've been riding for some time. Maybe 20 minutes or so. It's very bizarre and annoying.

forces me to loosely hold the clutch so it revs a little lower in first...

thanks!

Check the placement of the spring (carb side) of your choke cable. The PO I bought my bike from had put the spring between the end of the cable, and the end of the housing, meaning the choke would close, but not all the way; bad acceleration and weird idle issues were the trigger.

Quote from: anoopb on August 20, 2012, 08:14:01 AM
forces me to loosely hold the clutch so it revs a little lower in first...

This exact thing was happening to me during my clutch testing recently.  I had an issue with my clutch cable not getting locked tight enough in one or more places, so after a short time riding it would start to come loose and this was integral to the last part of my test drives.  For some reason as my clutch lever would loosen, this would happen more and more; to the point that I would have to hold the clutch in nearly at the friction zone to get the RPMs to drop to an appropriate idle.  For me the fix was to check my clutch release adjustment screw (under the 2 screw side-panel above your gearshift lever) and adjust the freeplay appropriately, and most importantly made sure all adjustment screws were tightened securely.

Quote from: Janx101 on August 16, 2012, 10:57:19 PM
could also be sticky choke cable if its affected by moving the bars

It could simply be the routing of your cables causing some of this too.  Especially if you've had your gas tank off recently, you might want to just check and make sure that things are routed the right way, and that nothing is tie-wrapped down too tight (leave a slight amount of wiggle room so they can adjust themselves as the handlebars turn, etc.).  This could apply to any of your 4 cables (accel/decel/choke/clutch).


The thing that throws me a little is that it happens after getting warmed up and seemingly goes away when cool.  That might not be cable issues...but it still doesn't hurt to rule things out.

I have noticed some bikes developing a high idle when hot. Slipping the clutch brings it back down.

I've asked the question before. All I ever hear is "vacuum leak". However,on any affected bike, spraying the crap out of it with WD40 or starter fluid or carb cleaner has no effect. There is no air leak. There is no vacuum leak.

Swapped carbs with exactly the same thing happening.

I have examined this with the tank  off and bike on center stand. Choke is not the cause. Throttle cable is not the problem. Both are free and operate with ample free play.

Carb slides drop down where they should be (looking in airbox with filter removed).

Air filter in or out has no affect.

I can put my hand over the air intake to drop the RPM's. Then they stay down until the throttle is blipped again.

adidasguy and NicroHobak

this is exactly what you're describing. it annoys me to no end.

all i ever heard was vacuum leak as well. I took it to the shop and they did the "mechanics special" on it and the guy didn't say anything about a vacuum leak.

NicroHobak, so you did manage to find a fix. that's good.

I'm going to look at the clutch cable tonight and see if there is any give.

I still don't understand how the clutch could cause the engine to rev so high though.

I'm having exactly the same problem -- high idle ~3k rpm after the bike warms up.  It seems more like AdidasGuy's description, though, in that the cables don't seem to be involved.

I'm working on a stumbling issue right now, but I've been trying to give this one some thought, and I have a half-baked idea I'd like to throw out there.

What's interesting is that the higher idle seem to be around 3000 on different bikes, so it seems like this is something in the design of the bike, not some peculiarity of individual bikes, and it mimics holding the throttle open a little.  Also, and I can't say this for certain, but it seems like the high idle happens when the engine rpm's are coming down, not as an increase from normal idle.  So, I'm thinking carburetor.

Carburetors normally work by negative feedback -- an increase in air velocity raises the slides which decreases air velocity -- but I'm wondering if the high idle is an unintended positive feedback loop.  Under certain circumstances (size of the jets, pilot screw settings etc...), as the engine rpm's decrease, you may have a brief excess of gas in the carbs or in the intake manifold, which would tend to keep the rpm's up.  I'm thinking that there may be a balance point ~3000 rpm where that excess keeps the rpm's up, which in turns pulls enough air through the carbs to keep the air-gas mix flowing beyond idle levels, which keeps the rpm's up, and so on.

I think this might also explain a few of the observations:
- slipping the clutch forces the rpm's down and breaks the loop
- covering one carb intake lowers the airflow and breaks the loop
- blipping the throttle could pull in excess air-gas without giving the carbs time to inject more, which might break the loop
- a warm engine tends more toward richness (I think), so the loop might be more likely to start

As a guess at a possible solution, which unfortunately I'm unable to test at the moment, maybe making the idle mix leaner would prevent the loop from starting.  My understanding of carburetors is still pretty basic, so this might make no sense at all.  But, maybe it will give more experienced folks some ideas.

noob: maybe you misunderstand our reference to the clutch.

When I say "slipping the clutch" I mean I slightly release it when stopped to drag the engine, lowering the RPM's. When on the center stand testing, I don't ever put in gear. I put my handover the air intake to bring the RPM back down.

For me the high RPM's tend to be a little above 3000. I have had it go up on its own - once in a while, when really hot. It is a slow rise over 5 seconds.

Too rich might be a possibility. And when hot there is better combustion so it feeds on itself. I have never had a throttle blip bring the RPM back down.

Quote from: adidasguy on August 20, 2012, 01:27:04 PM
I have never had a throttle blip bring the RPM back down.

If I try blipping the throttle right after the high idle starts, it usually doesn't (maybe never) works.  But if the high idle goes on for a while, it seems, for me anyway, that blipping has more of a chance of working.  I haven't really tested that statement, but it's my general impression.  Trying to fit that into the positive loop idea, the longer the high idle goes on, the more excess gas on the intake side is used up, and the more likely a blip is to break the loop.

Positive loops are generally unstable, although they can have a balance point -- it might not take much to prevent it.

Quote from: anoopb on August 20, 2012, 11:47:13 AM
adidasguy and NicroHobak

this is exactly what you're describing. it annoys me to no end.

all i ever heard was vacuum leak as well. I took it to the shop and they did the "mechanics special" on it and the guy didn't say anything about a vacuum leak.

NicroHobak, so you did manage to find a fix. that's good.

I'm going to look at the clutch cable tonight and see if there is any give.

I still don't understand how the clutch could cause the engine to rev so high though.

I had the same problem you're having when I bought my bike.  The PO had the idle screw too far in.  The bike ran fine until it warmed up, then the idle started surging when in neutral/clutch in.  When in gear/moving it ran find because the engine was connected to the wheels.  Backing the idle screw (wayyy) out fixed the problem.  However, I found out he'd had it set that way because the engine would not run otherwise...the valves were wayyy out of spec (tight).

Once the bike warms up and your idle starts surging, back out the idle screw until the bike is at a steady ~1300 rpm.  I suspect this will solve your problem.  If after doing this your bike runs like shaZam! when cold, requires constant idle adjustment and takes forever to warm up, I suspect you might need a valve adjustment as well.  I should note that the PO of my bike thought an air leak was causing his problems when he sold me the bike, as they have similar symptoms.  When you say that this only happens when the bike warms up it throws a red flag...cables don't just stick when the bike warms up.  They stick or they don't.  This sounds more engine-related.

Leadberry,

This was it. Sure enough I adjusted the pilot screw as it got hot and that fixed it.

Unfortunately, because i'm a newb, i've had to almost relearn all of the bikes little nuances all over again.

What's the idle speed (when warmed up fully) supposed to be on a GS500E?

thanks!

Anoop

1200-1300 rpm.

the high idle after she warms up sound like an air leak..Is she also slow to return to idle?

If you turn the bars and the engine rpms rev or change i would certainly check choke and throttle cable travel and lubricate them..

I just wrote this on another thread, but check the carb boots and make sure you didn't crimp the edges of them when you installed the airbox.  i have seen this happen a lot and its very easy to get it wrong...Follow the boots all the way around with a flashlight to make sure there are no parts of the boots that are crimped or not seating over the airbox properly..You can actually pry the edges out so they seat correctly with a flathead or i have also seen them pulled back over the airbox with needle nosed pliers, but it is hard to get in there with pliers and i have found a flathead to be easier...Be careful not to put a hole in them!..

Have any of you checked that your cables are not wearing out internaly ,in other words the wires in side get hard with use and start breaking one by one they then stick into the inside of the cable liner stopping the cable doing its job . some times they go at the nipple and  other times deeper in the case where you cant see them .It was very commen in the 1960s -70s when the liner was made of metal and water used to get in and rust them if you didnt oil regualyAlot of problems on here are associated with older bikes with  very doughtfull maintance history..