Author Topic: 2009 GS500F Random High Idle  (Read 423 times)

Offline 2009nakedgs

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2009 GS500F Random High Idle
« on: March 20, 2020, 05:27:41 PM »
Hi guys I just recently purchased a 2009 gs500f. Ive put 1500 miles on it or so and ive been having a strangle idle issue where after the bike has been warmed up it will idle around 3000 to 4000 rpm. But it doesnt idle consistently like this. Ill come to a stop and half the time itll still go down to around 1,700. Sometimes it will then slowly climb back up to 3000. Other times I will come to the stop and it will be idling around 3000 anyway though. I had tested it with starting fluid for an air leak and it seemed to be the carb to engine intake boot. I replaced them both and just went out for a ride and it seemed that the issue had gone away but the issue returned about 45 minutes into the ride. I tried spraying the air box boots and the carb boots with starting fluid and couldnt seem to find any leaks. I doubt its the valves but i will be checking those soon anyway as im nearing the service interval. Any thoughts or ideas are appreciated. I just want to get this issue fixed so i have more peace of mind with the bike and dont have to turn the engine off at stoplights to avoid overheating.

Offline mr72

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Re: 2009 GS500F Random High Idle
« Reply #1 on: March 20, 2020, 05:29:52 PM »
The idle is set too high.

Set the idle mixture and speed according to this:

https://joshkarnes.blogspot.com/2017/09/fixing-common-gs500-carburetor-issues.html


Offline The Buddha

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Re: 2009 GS500F Random High Idle
« Reply #2 on: March 20, 2020, 05:33:29 PM »
Its a sign its lean Hot idle is high, cold idle is low - and it has to be 30-60 seconds after startup and taking off choke when you check it cold - but make sure its not sucking air, throttle cable moves free, choke isn't stuck, air filter box isn't letting in un filtered air, exhaust leak, valve adjustment is set right - and after being sure, pull the plugs after 2min hot idle, and if its white (and it can be) open up the mixture screws 1/2 turn.

BTW you got stock jets in it ? You may want to check float level as well before pulling it apart.

Cool.
Srinath.
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Offline 2009nakedgs

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Re: 2009 GS500F Random High Idle
« Reply #3 on: March 20, 2020, 07:33:14 PM »
I will try the instructions in that link you sent i appreciate it. And I did I fast check to see if the float heights were way out of whack by attaching a clear tube to the float bowl drain and held the tube curving up to see where the fuel level stopped on prime. They both held level pretty well so i dont believe the valve seat is leaking. But i was checking that because i have some fuel leaking out of my airbox drain hose. Im pretty positive the fuel petcock is the culprit for that issue though.

Offline 2009nakedgs

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Re: 2009 GS500F Random High Idle
« Reply #4 on: March 20, 2020, 10:08:44 PM »
Its a sign its lean Hot idle is high, cold idle is low - and it has to be 30-60 seconds after startup and taking off choke when you check it cold - but make sure its not sucking air, throttle cable moves free, choke isn't stuck, air filter box isn't letting in un filtered air, exhaust leak, valve adjustment is set right - and after being sure, pull the plugs after 2min hot idle, and if its white (and it can be) open up the mixture screws 1/2 turn.

BTW you got stock jets in it ? You may want to check float level as well before pulling it apart.

Cool.
Srinath.

And I am not the original owner of the bike the original owner cleaned the carbs at one point but mentioned nothing of swapping to bigger jets. Im considering swapping to the European jets anyhow as ive heard the americans are extra lean. Im completely unfamiliar with the mixture screws and how many adjustments can be made on this carburetor though which is a 2009.

Offline Bluesmudge

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Re: 2009 GS500F Random High Idle
« Reply #5 on: March 20, 2020, 10:35:35 PM »
Set the idle after the bike has warmed up and been ridden for at least 10 minutes. If you set it right after starting the bike then it will be too high once wared up.

Offline 2009nakedgs

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Re: 2009 GS500F Random High Idle
« Reply #6 on: March 20, 2020, 11:56:39 PM »
Set the idle after the bike has warmed up and been ridden for at least 10 minutes. If you set it right after starting the bike then it will be too high once wared up.
The idle is fine it just randomly climbs. And this is after about 30 minutes of riding recently. Before i replaced the carb to engine boots it would happen about 15 minutes after the bike was warm. But it still would rarely go down to the correct Rpm at idle. So that tells me it's an issue outside the actual idle adjustment screw/knob. From when I was in the machine i remember the screw was stopping the throttle as it should and it wasnt backed out to where there was a gap. So i believe the idle adjustment knob is alright at least for the time being. Im going to research more about the idle mixture screws and which go to what jet
« Last Edit: March 21, 2020, 12:52:58 AM by 2009nakedgs »

Offline The Buddha

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Re: 2009 GS500F Random High Idle
« Reply #7 on: March 21, 2020, 01:00:33 PM »
Yea the euro/non EPA - however by 09 all the countries were just as bad as US spec. Which is why we jet it to +1 on pilot main and needle. And set air screws to 3 (from 2.5). That effectively is "euro" because that was the euro spec of 89-2000. Now I never looked in a post 01 factory manual. So no idea what it says.

I have however seen bikes where everything was fine, no leaks anywhere, valves in spec etc etc that will not hold that 100 rpm difference between hot and cold idle. They also burn their plugs white. You have to set the idle hot yes, but you should not lose more than 100 rpm from that number to the 1 minute after starting on choke. That is my definition of cold idle. And plugs read chocolate color.
Back in 1995 when I first started fighting with my used 89 the mechanics I spoke to at dealers etc all used to say, the minute anyone complains about warm up and running etc on a new bike, we tell them it needs a jet kit. That wasn't all that cool with me, so I fought that idea. Come to find out My bike had 42.5 pilots in it, 2 sizes up from stock. Cos it has 42.5 air jet and some dummy thought the pilot was supposed to be 42.5 and swapped it for that, the bike would burn plugs black and fall on its face when trying to take off, but get it past that and it ran a lot better than most stock bikes. Thanks to the 125's in it. Finally when I realized it 2 yrs later, I couldn't find 40's. I eventually found them and started getting good results etc etc. The equivalent on an 09 is 20 vm style and 132.5 small round slotted.
You definitely have to find all the other problems if any like I said, but don't be shocked if all that gives you nothing that will solve this problem. Setting it after hot and not cold etc etc etc is all fine if you're seeing dark tan-chocolate colored plugs. If you're seeing white plugs - you're still lean, you've just set it to only idle after it gets super super hot. 1 min on choke and hot idle should be no more than 100 rpm apart. That was how the pre epa bikes with stock original carbs behaved. You cant even jet those any better. A 1983 nighthawk for example - which I bought a pristine stored indoors flawless model in 1996 with barely 1200 miles did that exact thing - 100 rpm between 1 min and 1 hr after riding. I could twist the GS's idle screw till I was blue in the face and never get that till I went to 40/125 - with 42.5 it would do that 100 rpm perfectly, but it would fall on its face at take off.

Cool.
Buddha.
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Offline 2009nakedgs

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Re: 2009 GS500F Random High Idle
« Reply #8 on: March 24, 2020, 12:56:39 AM »
Thank you for the info. I was riding the bike yesterday and when the idle issue occured i sprayed starting fluid around everything again and when i would spray around the carb boot the idle would drop from 3000 to normal idle. Then today i try the same thing but i cannot get it to change idleno matter where i spray it. I ran out of that and started spraying diesel on stuff to see if that would show anything and it didnt. So i really am confused with what could be happening. Yesterday when it was showing signs of a leak with the fluid it was repeatable results but today it wouldnt even do it. And those mixture screws have epa caps on them. Ill take thos epfd but im leery of messing with any settings until i know this isnt some air leak. Its messing with my head haha. Also something i notice is when i turn the bike off and then back on it started at normal idle and then i covered the air filter opening with my hand partially. This was effectively choking the motor which raised the rpm to around 3000 but when i took my hand away it stayed at 3000 rpm. Did not touch the throttle
« Last Edit: March 24, 2020, 01:09:08 AM by 2009nakedgs »

Offline mr72

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Re: 2009 GS500F Random High Idle
« Reply #9 on: March 24, 2020, 02:40:54 AM »
I say again: your idle is simply set too high.

You may have other problems like vacuum leaks (likely) or lean idle mixture (almost guaranteed) but those are not the CAUSE of the variable idle, your problem is setting the idle too fast.

Take out the plugs on the pilot mixture adjustment and set the idle mixture and speed correctly with a FULLY WARMED UP bike. That is 10-20 minutes of ACTUAL riding and going through the gears.

Offline Meukowi

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Re: 2009 GS500F Random High Idle
« Reply #10 on: March 24, 2020, 06:36:09 AM »
in a perfect condition youd have the idle screw unscrewed all the way down, so run it hot and adjust idle from there. i have about 1/4 - 1/2 turns in

Offline Bluesmudge

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Re: 2009 GS500F Random High Idle
« Reply #11 on: March 24, 2020, 03:25:18 PM »
When the issue occurs, have you tried simply lowering the idle speed with the idle speed adjuster instead of spraying diesel all over the bike?

Set the idle after the bike has warmed up and been ridden for at least 10 minutes. If you set it right after starting the bike then it will be too high once wared up.
The idle is fine it just randomly climbs. And this is after about 30 minutes of riding recently. Before i replaced the carb to engine boots it would happen about 15 minutes after the bike was warm. But it still would rarely go down to the correct Rpm at idle. So that tells me it's an issue outside the actual idle adjustment screw/knob. From when I was in the machine i remember the screw was stopping the throttle as it should and it wasnt backed out to where there was a gap. So i believe the idle adjustment knob is alright at least for the time being. Im going to research more about the idle mixture screws and which go to what jet

The idle is not fine because it "just randomly climbs." Since it happens 30 - 45 minutes into your ride, don't set the idle until you get to that point as apparently thats how long it takes for your bike to warm up enough.

Your bike probably starts up fine with little to no choke. That is not normal. Your idle is set too high.
« Last Edit: March 24, 2020, 03:30:19 PM by Bluesmudge »

Offline The Buddha

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Re: 2009 GS500F Random High Idle
« Reply #12 on: March 25, 2020, 12:00:04 AM »
You guys can fight this however hard you like. Soon enough, it would be like fighting gravity.

I would say 30 sec in summer and 1 min in winter it would need to hold an idle rpm. 1 hr after a ride, if it doesn't hold that same rpm + 100 or less - you will be burning white at the plugs. You're at that point fighting physics.

Sequence of events is this -

Set idle wherever you like. Write down the rpm.
Ride however long you like. Write down the rpm.
Turn it off and go to sleep.
Wake up and start it on choke.
1 min later take it off choke. Write down rpm.

Are the 3 rpm's within 100 of each other > Yes - Pull plugs. white > open fuel screw 1/4 turn. Black - leave it alone. Choclate definitely leave it alone.

Are the rpm's over 100 apart ? Yes - Pull plugs - white - yea open fuel screw. Black ? Oh wait where was the rpm off ? Lower when hot ? then close mix screw 1/4 turn.

Repeat.

Cool.
Buddha.
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Offline 2009nakedgs

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Re: 2009 GS500F Random High Idle
« Reply #13 on: March 26, 2020, 01:03:56 AM »
Im going to go with the buddhas advice here. Im going to do one more air leak test just to be sure before removing my epa caps and getting to it. And the bike does need full choke for about a minute to idle without dying. When the bike is fully warm with over an hour of riding when the idle chooses to be correct it idles around maybe 1,700 opposed to the 1,100 rpm cold idle so according to the buddha thats out of spec. Then the idle will just climb out of nowhere to 3k rpm or it will hang there. Ive also wondered if it could be a worn diaphragm or a sticking slide possibly? But the raising of the idle from idle rpm to 3k at a stop wouldnt make sense to be a sticking slide i suppose as i would need to give it gas to raise the slide for it to stick.

Offline The Buddha

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Re: 2009 GS500F Random High Idle
« Reply #14 on: March 26, 2020, 01:42:39 PM »
Yea make sure you dont have a leak. Now also do a plug pull at idle.

Your slide can stick all it wants, if the throttle is shut rpm will drop, if the slide is sticking it largely is irrelevant your butterflies at shut throttle should close nearly to fully shut making the only fuel input coming from those tiny holes that pull through pilot and those air intake holes in the filter side. Now make sure they are synched when you're pulling the carbs, set floats as well. Sticking slides may be a bigger problem when opening throttle and it doesn't rise, or its up higher already and lets in too much air. Try this experiment - with the bike idling don't touch the throttle, stick you hand through the air filter housing and lift a slide. You'd see it does nearly nothing.

Anyway, a rip in the diaphragm will prevent the bike from getting over a certain throttle position even when you open it. If you find it runs fine to 1/2 throttle and doesn't gain rpm past that, that's how the rip affects it. You'd make 7k in 1st gear @ 1/2 throttle, 6 in 2nd, 5 in 3rd 4k in 4th and never get it moving well enough to get into 5th or 6th. And it will behave perfectly till that wall is hit, and burn the plugs dependent on jetting - if it was chocolate, it will stay chocolate.

Random rising idle is lean, so is that 600 rpm difference. Sometimes if the rpm will not drop - it can be a sticking cable, but not usually when it rises at random. BTW worth while checking cable lube, play and binding etc  when you're eyeballs deep in carbs.

Cool.
Buddha.
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Offline 2009nakedgs

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Re: 2009 GS500F Random High Idle
« Reply #15 on: March 28, 2020, 02:51:13 PM »
Yea make sure you dont have a leak. Now also do a plug pull at idle.

Your slide can stick all it wants, if the throttle is shut rpm will drop, if the slide is sticking it largely is irrelevant your butterflies at shut throttle should close nearly to fully shut making the only fuel input coming from those tiny holes that pull through pilot and those air intake holes in the filter side. Now make sure they are synched when you're pulling the carbs, set floats as well. Sticking slides may be a bigger problem when opening throttle and it doesn't rise, or its up higher already and lets in too much air. Try this experiment - with the bike idling don't touch the throttle, stick you hand through the air filter housing and lift a slide. You'd see it does nearly nothing.

Anyway, a rip in the diaphragm will prevent the bike from getting over a certain throttle position even when you open it. If you find it runs fine to 1/2 throttle and doesn't gain rpm past that, that's how the rip affects it. You'd make 7k in 1st gear @ 1/2 throttle, 6 in 2nd, 5 in 3rd 4k in 4th and never get it moving well enough to get into 5th or 6th. And it will behave perfectly till that wall is hit, and burn the plugs dependent on jetting - if it was chocolate, it will stay chocolate.

Random rising idle is lean, so is that 600 rpm difference. Sometimes if the rpm will not drop - it can be a sticking cable, but not usually when it rises at random. BTW worth while checking cable lube, play and binding etc  when you're eyeballs deep in carbs.

Cool.
Buddha.

Awesome thanks for the time and advice. I will do all this. I will post with my findings. I will be checking valves at about the same time just because its past its interval.

Offline The Buddha

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Re: 2009 GS500F Random High Idle
« Reply #16 on: March 28, 2020, 10:46:11 PM »
A slightly tight valve will start up perfectly and 5 seconds after start up will want to die unless you kept revving it, till about 5 mins later when it would run like a dream. Till you shut it off and it cools down 1/2 way. Cold valves that are close to 0 clearance will actually have higher clearance when warm, but they don't warm up evenly. The valve heats up faster causing near 0 clearance to go negative and hence will be hanging open when warming up, but in 2-5 mins the head warms up too, and turns that negative clearance back to positive and gets the valves closing again.
Anyway check it, but not a cause of random revving up.

Cool.
Srinath.
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