Weird idle issue - 2006 GS500F

[Dr.McNinja]

Hey everyone,

Figured I'd make my first post amazing, so here we go -

Forenote: The bike is basically new (~490 mi. when it was bought). It sat in storage for a while and wasn't properly taken care of.

Me and a friend went to clean the carbs and we chickened out half way (carbs weren't off) and replaced everything. The guides for GS500F carb removal are lackluster and we didn't want to continue blind. So, we put the airbox back in, plugged everything in, and went on our way. We replaced two weather-cracked fuel lines which solved a fuel smell that was fairly obvious. Along the way we did muscle the carbs around, but couldn't get them unseated, which was the point when we chickened out.

Now the bike has a problem it didn't have before. If I come to a stop the engine revs high with zero choke. However, if I do not touch the throttle as I'm coming to a stop the engine will idle around 1,200-1,500 RPM (factory specs). It's only after I rev the engine does the engine RPMs go up and stay around 3,200. Interestingly enough I can bring the engine speed back down to regular idle by feathering the clutch for a second. During riding the bike doesn't seem to be riding in a higher RPM range than usual. However, at the stop lights I can consistently reproduce this problem.

My first instinct is that I'm pretty sure we placed the fuel lines wrong. It runs in RES and lags to a stall in ON and since RES is where PRI is run from, it should run from there. I'm going to swap them after I'm done typing this. Which fixes that problem.

As far as the problem is concerned it doesn't seem to have any indications of a intake leak. The idle doesn't stay high at all. It will come back down after feathering the clutch and stay steady after that. It's only after I blip the throttle at a stop will it stay high like it's choked, even though the choke is fully off.

Second thing I'm almost positive I eliminated is throttle stick. The throttle is very responsive and if I try to get the bike to jet off the stop line when the idle is high it will die unless I actually twist the throttle to keep engine speed up.


The only two things I'm not certain of is if the choke is potentially stuck a little open, or the choke needs adjustment. Likewise, I'm curious whether or not adjusting the idle when I blip the throttle so it goes back down to normal would be beneficial at all or it would just lead to a stall unless I'm constantly blipping the throttle.


I also would wager it could be the air valve under the gas tank getting loose, but I'm not certain if that would cause this or not. I know there's a vacuum hose on the left carburetor, but I haven't checked it. I'll check it tonight when we take off the tank.


Does anyone have any experience with this? I'd rather not have to order a Hayne's manual and work my way through a full carb rebuild if I don't have to. I'd really appreciate any feedback, I'll be more than happy to test any suggestions or go out and test different things to give you guys a better idea of what's wrong.

Thanks!

[Big Rich]

Lube your throttle and choke cables for now- just wd40 or something will work better than nothing.

And did you take the float bowls off yet? If not, do that and clean them at least.

[Dr.McNinja]

I haven't. Took it out for a ride today -


Checked the tank. Everything is plugged in correctly. Idled perfect for the first probably 45 minutes of it being on. No problems at stops or anything. It appears after about an hour of riding the idle gets progressively higher, peaking at around 3,700. This isn't a big deal, except I went into a few turns today with the bike's engine speed definitely too fast. I don't encounter this problem when I have to downshift but for a quick turn in the same gear this is very evident. It's almost too dangerous to ride it unless I take turns at granny speeds once the idle starts getting bad. All the plugs are plugged in correctly and there are no visible air leaks. I would think that an intake leak would be present at all times, and not just after being on the road for an hour or so. The only thing I could think of now is a rotted o-ring or something that does it's job cold but once it starts expanding it screws everything up.

I don't know anymore. Could it be a misadjusted choke/throttle from when we moved the carbs and cables around a bit before reseating them?

When I was riding home I was able to take my hand off the throttle and have the bike essentially ride itself in first. Which is really bad. To me, that's the only symptom of a sticky throttle even though the throttle snaps and has a normal amount of play at the handle bar.


I really don't want to have to take it to a dealer. It's probably gonna be well over 500 dollars for the entire thing with all the added "magical" problems the dealers create to make money, which means I'll be boxing up my bike until I can afford to take it in on a college kid's salary. Let me emphasize I really don't want to do that.

[Big Rich]

Only other thing I can think of is the carb boots are warming up and expanding (causing an air leak).

[Dr.McNinja]

Only other thing I can think of is the carb boots are warming up and expanding (causing an air leak).

I wish that I could find OEM carb boots. I can't find any anywhere. I had the same suspicion.

We did yank on the carbs a little to try to unseat them and they didn't 'seem' to budge, however, it may have been enough to unseat them. We didn't bother to push them back in at all because they didn't seem to move. Unfortunately this problem occurs way late into the ride so it makes it hard to check for the leak. If you have a suspicion this could be the problem it would be fairly trivial to take the bike down again and push the carbs in as hard as we possibly can while tightening them.

[crzydood17]

go for a long hard ride for 20-40 mins... then re-adjust your idle down to 1100-1200. If that doesn't solve your issue then grow some balls and pull the carbs. They should come off easy enough push them down and pull up a few times and the heat bond should break. Pull off your float bowls and check for gunk pull out the 3 jets from each side and blow them out. Take the carb boots off the head and check for major cracks. while you got all that crap taken apart grab some starter fluid and put the little straw into the 2 holes under the carb intake and blow those bad boys out. throw it all back together, prime it check the float levels. Reset your idle after another longer ride. If that doesn't fix it, grab the starter fluid and cover the entire engine and light it on fire...

[justinmc84]

Really, pulling carbs off isn't as scary as it seems.  I had the same sentiment you have now before I took them off and cleaned them, but really if you're careful, do 1 at a time, and make sure you have everything pulled correctly it's not too bad.  My fears derived from it being such an important part of the bike, one of the parts that can cause all sorts of gremlins, and my lack of experience.  But with the guides here (search is your friend) you can accomplish taking the carbs off and cleaning them.

And if you run into any questions, pretty much everyone here has done it 1 time or another so just ask.

[mike__R]

I don't know why you wouldn't want to get the Haynes manual...........go for it and it will help walk you through a lot of things on the bike..........definitely recomended.

[BaltimoreGS]

If you pull the carb, drill the brass caps and adjust the pilot screws.  If they are out of adjustment it can lead to your hanging idle problem.

-Jessie

[Dr.McNinja]

go for a long hard ride for 20-40 mins... then re-adjust your idle down to 1100-1200. If that doesn't solve your issue then grow some balls and pull the carbs. They should come off easy enough push them down and pull up a few times and the heat bond should break. Pull off your float bowls and check for gunk pull out the 3 jets from each side and blow them out. Take the carb boots off the head and check for major cracks. while you got all that crap taken apart grab some starter fluid and put the little straw into the 2 holes under the carb intake and blow those bad boys out. throw it all back together, prime it check the float levels. Reset your idle after another longer ride. If that doesn't fix it, grab the starter fluid and cover the entire engine and light it on fire...

I have a can of Berryman's B12 I can spray into the carbs from the airbox. However, my fear here is that the idle adjustment will cause my bike to die without tons of choke except for when it's super warm (30-40 min later). This seems more like a bandaid than a fix. But it's worth a shot if nothing else works.

Really, pulling carbs off isn't as scary as it seems.  I had the same sentiment you have now before I took them off and cleaned them, but really if you're careful, do 1 at a time, and make sure you have everything pulled correctly it's not too bad.  My fears derived from it being such an important part of the bike, one of the parts that can cause all sorts of gremlins, and my lack of experience.  But with the guides here (search is your friend) you can accomplish taking the carbs off and cleaning them.

And if you run into any questions, pretty much everyone here has done it 1 time or another so just ask.

Most of my fear isn't taking off the carbs and ruining something. We ended up chickening out mostly due to the dry rot on alot of the tubing. I didn't want to tear something and brick my bike for a few weeks while I scour the internet for a 2006 GS500F carb rebuild kit and a carb disassembly manual. The one off the GStwins website is the one we tried using, but it's not very descriptive, and I'm pretty sure the Mikuni carbs on the newer models are different.

Syncing the carbs seems easy enough. Not that I want to do it yet, but I may as well ask the question now. Are the two valves on the top of the carbs not hooked up to the upper T (the two valves that are left open) the adjustment valves? I understand you sync them by vacuum, and most newer carbs have specific adjustment valves that you can plug in to. On my bike these valves I speak of now have no covers and both face the left on the top of the carbs looking down from the gas tank side. I also understand the screw-looking thing between the carbs is the adjustment screw, and you twist it either way until the vacuums are even.

If the fact the left side upper valves aren't hooked up vs. the right side upper valves (right side has the T connected to it) as I stated above could be considered a problem - let me know and I'll get the digital camera out and take a picture when I get home from work for clarification. I could be describing it all wrong.

[lamahug]

My 2004 GS500F has your exact same idle problem - it revs high at 3200 rpm after it has warmed up.  It goes to 1100 rpms when you first take it off choke, then, by itself just sitting there, after about six or seven minutes, it slowly climbs to 3200 rpm.  When riding around, it usually idles at 3200, but sometimes, it will idle down to 1100.      I have gotten used to it, but should get it fixed.  Please post your fix to your idle problem when you get it all sorted out.

[crzydood17]

changing the idle down to 1100-1200 after its completely warm is in no way a bandaid its the correct and factory way to set a idle. If the idle is set just a bit too high it can cause a hanging idle...

[Dr.McNinja]

changing the idle down to 1100-1200 after its completely warm is in no way a bandaid its the correct and factory way to set a idle. If the idle is set just a bit too high it can cause a hanging idle...

This is interesting. Would that "complete warm up" be that 45 minute mark? That would explain a lot. We've screwed around quite a bit with my idle. I have no doubts I need to clean my carbs,  but this could definitely be possible.



Good news though guys,


Today I rode the bike around with my girlfriend for about 30 minutes, started getting the hanging idle problem, took her back to the house and shut down and restarted the bike. Held it's idle at 1,500 and I took a WD40 can (which is apparently safe on rubber) and sprayed around the intake manifolds (engine side) and paid attention for changes in engine sound. Re-revved the bike so it hung and then sprayed again. Nothing. Sprayed a few areas around the location where the carbs and the boot are locked in by the clamp and nothing. No engine changes. I'm thinking this rules out a intake manifold leak. Especially considering WD40 is flammable it should've caused at least a minor increase in engine speed briefly. When we open up the bike again tomorrow I will spray more thoroughly and try to spray the air hoses as well as the manifolds leading to the airbox. But so far, nothing.


We're going to tackle the problem like this

Adjust throttle -> Adjust Idle (as suggested) -> Adjust choke (if it's stuck) -> Remove the tank and spray WD40 looking for leaks -> etc.

If the idle/cable adjustments fix it, we'll probably tackle the carb problem with some Berryman B-12 ChemTool and then pursue a more permanent fix once my Hayne's manual arrives. Otherwise, I'll be continuously updating this thread until the problem is solved.


I'll post things as I go, but I'd appreciate feedback from the more experienced members. It would be a great help knowing I'm approaching things the right way.

My 2004 GS500F has your exact same idle problem - it revs high at 3200 rpm after it has warmed up.  It goes to 1100 rpms when you first take it off choke, then, by itself just sitting there, after about six or seven minutes, it slowly climbs to 3200 rpm.  When riding around, it usually idles at 3200, but sometimes, it will idle down to 1100.      I have gotten used to it, but should get it fixed.  Please post your fix to your idle problem when you get it all sorted out.

The documentation on the gs500 wiki regarding the 04-08 GS500FK's is severely lacking. I plan on documenting everything I do.

[Dr.McNinja]

Double post - damn internet. Mod please delete this one.

[Big Rich]

Watch what you do with Berrymans- it, like most carb cleaners, can damage rubber.

While a complete carb tear down is always best, I think the majority of your problems are just in the float bowls and jets. All of which can be removed and cleaned with the carbs still on the bike.

[Dr.McNinja]

Watch what you do with Berrymans- it, like most carb cleaners, can damage rubber.

While a complete carb tear down is always best, I think the majority of your problems are just in the float bowls and jets. All of which can be removed and cleaned with the carbs still on the bike.

Would you happen to know of any guides on properly adjusting the choke/throttle cables and how to insure that they aren't getting binded anywhere from when we moved them to access the carbs/airbox?

Before we try adjusting the idle or anything involving removing the gas tank, the first thing we're going to do is adjust the cables.

[Big Rich]

Not for a GS500- I don't own one........

Why do you want to adjust the cables? Aside from a sticky cable that I mentioned earlier (which I don't think is an issue anymore), there shouldn't be any need to at the moment. I stick to my prior advice about the float bowls and jets.

[Dr.McNinja]

Not for a GS500- I don't own one........

Why do you want to adjust the cables? Aside from a sticky cable that I mentioned earlier (which I don't think is an issue anymore), there shouldn't be any need to at the moment. I stick to my prior advice about the float bowls and jets.

I guess it's because I don't see why the problem wouldn't exist all the time if the carbs and jets were really screwed up. Shouldn't it idle high/run lean all the time if the jets and float bowls are messy?

Don't take this as me doubting your advice. I'm just having trouble visualizing why the problem isn't consistent from the start. More for my learning so I can spot this problem easier if it is indeed it.

[Big Rich]

Have you taken it for a longer ride then adjusted the idle afterwards? That's probably the fix.

Like I said- I don't own a GS. But my GR's don't take anywhere near 45 minutes to get fully warmed up. That's why I think you need to clean the carbs. You said the bike sat for a while (gas starts to go bad in as little as 3 weeks) and you said the bike has low miles (which is why I haven't said to check the valves). If you don't want to pull them off completely to do it, fine. Most of the problems you will have are in the jets and/or varnish in the bowl.

The most usual problems with cables are apparent when you turn the handle bars. If the engine speed increases but lowers, it's your throttle cable. If it increases and stays, it's the choke cable.

[Dr.McNinja]

Well I started running some Berryman's B12 through it.


The gas bubbling part scared the living f%$k out of me. It's supposed to do that though I guess, Berryman's eats up the styrene in the gas.



New problems have arised though and I can't diagnose them as me needing to adjust my idle because the carbs are cleaner, or my bike exhibiting more signs of dying.


Took the bike out for a ride yesterday. Ran fine. Idled a little low but the hanging idle problem still existed.

Took the bike out today. Didn't let it warm up enough, around 5 minutes. The ambient temp is about 95 degrees, I figured it was fine. Got bored and decided to joy ride it around the block a bit to warm it up at about 1/2 choke. The bike started backfiring like mad. If I revved the throttle I'd get one or two and then it would stop. During idle it didn't backfire at all. I noticed the choke's RPMs at full-open were 1k less than normal (it would normally choke at around 4-5k).

Let it rest a minute and then went back to riding. Took it on it's first turn after being fully warmed up (~10 minutes later) and the bike died in the turn. Sputtered, popped once or twice, and died. Restarted it and made my way home. The throttle didn't seem unresponsive, however the acceleration was noticeably deadened. It started to act "normal" by the time I arrived home. There was no popping on the main roads, the bike seemed responsive until I released the clutch as I began my turn at which point the bike would seem to loose forward momentum and no amount of throttle would get the bike to speed up quickly. This being said gunning it in the straights was easy.


This sounds like the bike is really lean now. I'm thinking it's for sure an intake leak, and it's getting worse by the day. I'm almost 100% certain the berryman's didn't cause this because I ran it for two days with berryman's in the tank and didn't have a problem at all. I checked the tank, and judging by the miles I have on the odo so far (~60 since the last fill) and the average I get (~150 per fill) I'm still just a hair over 1/2 full. I followed the berryman's by the book, ~1 oz per gallon of fuel and I added about 2.5 oz to a tank of 3.5 gallons.



I'll take it out for a short run tomorrow. If it doesn't fix itself I'll start calling mechanics around town. Figured I can't lose, if it's any more than 600 dollars to repair I'll just do it myself. Just wish I could've got a few more months into my favorite season (Winter) before I had to come to something like this. As for the carb boots needing to be replaced (highly likely) - are item numbers 20, 21, 22, and 23 what one would consider the carb-head boot? I'm almost 100% certain they are, but I'd rather ask here than spend 40 bucks in vain.