Author Topic: Adjusting idle screw, having to choose b/n hanging idle and bike dying when stop  (Read 965 times)

Offline BikerBoy

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So like the title says, Im adjusting my idle screw as I put in 135/60/20 jets and a K&N drop in air filter.. my bike either runs well, but will die when stopped without the choke on, or it stays running, but has a hanging idle...theres no sweet spot between them. The hanging idle goes away when I adjust the idle screw to under 1000 RPMs at idle, but then the bike dies when I stop it with no choke.

I havent adjusted the 2 air screws, 1 for each carb. I have the adjustable ones so I can play with them easily. Right now theyre at about 3 turns out. Would the solution be to screw the air screws in slightly, half a turn at a time, to fix my hanging idle? Or do I turn them out?? Thanks in advance  :thumb:

Offline The Buddha

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Try opening up the air screws a bit. 20 is good for pilots on a stock or drop in K&N and pipe, in fact 20 is ideal for all possible configs on a stock bore/stroke bike. You may need to go from 3 to 3.5 turn out on air mix screw - now if you're at 5+ I'd worry you are past its useable range, and may need 22.5.

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Offline mr72

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Hanging idle is because idle is too high. If it won't idle when it is completely warmed up then something may be clogged. The k&n drop in filter is not going to make it easier. Stockish jetting and stock filter will make life easier. K&n filter doesn't improve performance and filters worse than paper.

Offline BikerBoy

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Hanging idle is because idle is too high. If it won't idle when it is completely warmed up then something may be clogged. The k&n drop in filter is not going to make it easier. Stockish jetting and stock filter will make life easier. K&n filter doesn't improve performance and filters worse than paper.
Would taking off the restrictor on the air filter help (adding more air, leaning it out)??

Offline mr72

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That won't add more air. It'll just slow down the air and require different jets.

Offline The Buddha

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So like the title says, Im adjusting my idle screw as I put in 135/60/20 jets and a K&N drop in air filter.. my bike either runs well, but will die when stopped without the choke on, or it stays running, but has a hanging idle...theres no sweet spot between them. The hanging idle goes away when I adjust the idle screw to under 1000 RPMs at idle, but then the bike dies when I stop it with no choke.

I havent adjusted the 2 air screws, 1 for each carb. I have the adjustable ones so I can play with them easily. Right now theyre at about 3 turns out. Would the solution be to screw the air screws in slightly, half a turn at a time, to fix my hanging idle? Or do I turn them out?? Thanks in advance  :thumb:

Go to 3.5 richening it slightly. You're almost there if this is your only problem.
BTW K&N in the airbox is dirty as hell and the paper one is reuseable by washing it with gas and drying anf putting it back in, I don't even know why bother with K&N drop in.
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Offline BikerBoy

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So like the title says, Im adjusting my idle screw as I put in 135/60/20 jets and a K&N drop in air filter.. my bike either runs well, but will die when stopped without the choke on, or it stays running, but has a hanging idle...theres no sweet spot between them. The hanging idle goes away when I adjust the idle screw to under 1000 RPMs at idle, but then the bike dies when I stop it with no choke.

I havent adjusted the 2 air screws, 1 for each carb. I have the adjustable ones so I can play with them easily. Right now theyre at about 3 turns out. Would the solution be to screw the air screws in slightly, half a turn at a time, to fix my hanging idle? Or do I turn them out?? Thanks in advance  :thumb:

Go to 3.5 richening it slightly. You're almost there if this is your only problem.
BTW K&N in the airbox is dirty as hell and the paper one is reuseable by washing it with gas and drying and putting it back in, I don't even know why bother with K&N drop in.
Cool.
Srinath.

OK I did that yesterday, took the air filter out and put in the stock suzuki air filter, after cleaning it out with gas. I opened up the air screws a bit more and turned back down the idle a bit, but the bike actually runs worse, now it will start and idle, but even with the choke on it only goes to 1500 or 1600, and will die if you rev it above~3500 RPM (with choke on at idle) - it just dies (sounds like a COUGH and dies). I tried taking it for a ride to warm it up and maybe tune the air screws/idle screw once its warm, but if you try and go, it has ALMOST NO POWER. If you rev it too much while trying to go it just dies too. I messed with the idle screw, thinking it needed adjusting to get it to work, but I cant really get it to how it ran before.

I took the stock filter off and put the K&N one back on today but still has the same problem. I didnt change the jets or anything, and it ran pretty well before with this air filter, so it seems to almost certainly be an air screw/idle screw.

I need to reset the idle and air screws but dont know the procedure, can someone tell me how to reset it?? I made sure the carbs and everything were well connected today. thank you
« Last Edit: January 31, 2020, 10:44:51 PM by BikerBoy »

Offline mr72

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That sounds like the slides are not coming up. But idle mixture is the least of your issues.

Offline BikerBoy

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That sounds like the slides are not coming up. But idle mixture is the least of your issues.
The needle/valve seat slide next to the gas jets on the bottom of the carb, that needle? I took the carb off and their seemed to be more gas in it than usual, maybe the needle is getting stuck and letting more gas in idk. How would I fix that needle problem? thanks

Offline mr72

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no that sounds like the float needle valve. The slide is what you see when you open the throttle and look into the throat of the carb. It gets pulled upward by the diaphragm under the cap on the top of the carb by virtue of vacuum. When the slide moves up, it allows a higher volume of air to flow into the carb and also pulls up the needle from the main jet allowing fuel to come in that jet.

If the slide doesn't come up, then the needle stays in the jet and the bike will not rev or create power above a very low rpm/throttle.


Offline BikerBoy

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no that sounds like the float needle valve. The slide is what you see when you open the throttle and look into the throat of the carb. It gets pulled upward by the diaphragm under the cap on the top of the carb by virtue of vacuum. When the slide moves up, it allows a higher volume of air to flow into the carb and also pulls up the needle from the main jet allowing fuel to come in that jet.

If the slide doesn't come up, then the needle stays in the jet and the bike will not rev or create power above a very low rpm/throttle.
I see, normally when you turn the throttle without the airbox on, but with the carb on, you would see the slides move up if theyre operating properly right? Because when I took my airbox off and turned the throttle the slides didnt go up. So it sounds like you know what was wrong with it.

So the needle (the thing that you put a washer on) isnt moving up properly either I guess. Its weird because I didnt even touch the carbs I just swapped air filters and this slide situation happened.

anyone know if there a way of verifying the slides work with the carbs off the bike? Im wondering if some part of this need grease or something to keep the slides from getting stuck? thanks  :thumb:

Offline mr72

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If the slides are not coming up then most likely there is a huge vacuum leak, the diaphragms are damaged or incorrectly installed, or the slide and needle assembly is incorrectly assembled. Solution is the same, disassemble, inspect, reassemble ensuring everything is right.

Offline cbrfxr67

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sub'd to see how this plays out
"Its something you take apart in 2-3 days and takes 10 years to go back together."
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Offline The Buddha

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no that sounds like the float needle valve. The slide is what you see when you open the throttle and look into the throat of the carb. It gets pulled upward by the diaphragm under the cap on the top of the carb by virtue of vacuum. When the slide moves up, it allows a higher volume of air to flow into the carb and also pulls up the needle from the main jet allowing fuel to come in that jet.

If the slide doesn't come up, then the needle stays in the jet and the bike will not rev or create power above a very low rpm/throttle.
I see, normally when you turn the throttle without the airbox on, but with the carb on, you would see the slides move up if theyre operating properly right? Because when I took my airbox off and turned the throttle the slides didnt go up. So it sounds like you know what was wrong with it.

So the needle (the thing that you put a washer on) isnt moving up properly either I guess. Its weird because I didnt even touch the carbs I just swapped air filters and this slide situation happened.

anyone know if there a way of verifying the slides work with the carbs off the bike? Im wondering if some part of this need grease or something to keep the slides from getting stuck? thanks  :thumb:



Slides go up with the engine running as the rpms build when you give gas. They are not connected to the throttle cable in a CV carb, twisting it with the engine off don't do nothing.
More importantly if you can lift them with your fingers and feel air pressure above them, and let them go and they slowly sink back then its worth trying to experiment with it idling.
If they don't move up with your fingers or feel like you're crushing something - stop, you've incorrectly installed the spring on top of it.
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Offline BikerBoy

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I took the carbs off and verified the slides work by blowing compressed air in the holes in the slide and watching it move up like in this video: https://www.youtube.com/watch?v=lfQz4cxezAk

I put the carbs back on and inspected the vacuum lines, airbox boot, carb boot, air filter and airbox hoses to make sure theres no vacuum leaks. Drained the gas tank and carb and hose lines of all old gas (about 8 months old) and put in fresh gas. I then put on new spark plugs because the newish ones I put on last year already looked bad: I also put the original air filter on rather than the K&N one.

I also charged the battery fully and upon doing these things my bike fired up to 4500 rpm with the choke on. I'm not sure what exactly I fixed that did the trick. Going to adjust the idle and air screws next now that it seems to be running well again  :cheers:

« Last Edit: February 09, 2020, 09:14:27 PM by BikerBoy »

Offline The Buddha

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Well you do 40 things to fix 1 problem, you're playing roulette (which I believe was only done with a 6 shooter wasn't it).
Enjoy, don't worry about it.
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Offline BikerBoy

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Now that the bike runs again, I may have found a cause of my original issue, I bought the bike used and the air filter it came with is a HiFlo air filter not a Suzuki air filter. Some people here have had problems with them (http://gstwins.com/gsboard/index.php?topic=48170.0) so Ill buy a suzuki OEM air filter and see if it improves my idle issue
« Last Edit: February 17, 2020, 07:18:33 PM by BikerBoy »

Offline The Buddha

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I have Hi flow filtro in my GS, its not any different form the stock paper one just made a bit better. I would be very surprised if the filter is the problem.
Hi flow filtro is the brand name, its same flow filtro in reality.
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Offline herennow

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I'd agree, what year and country is your bike?

Offline BikerBoy

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I'd agree, what year and country is your bike?
Its an American 2008 gs500f with the fairings removed.

I replaced the air filter with a Hiflo and it seems to run much better, theres a ton of crap in the air here and the old one was probably blocked up. I have a new question though, concerning the 2 air screws under the carb I replaced with extendeable ones from ebay.



Its very convenient to be able to unscrew them without taking the carbs off the bike. It also allows me to measure how far out the screws are, so I can ensure the air screws are synchronized. However I have a small problem, the vibration from the bike tends to unscrew them a little bit. I was thinking, maybe they sell springs with more tension in them? This would keep the screws from bouncing around while I ride. Ive never used loctite before, would this be good to keep them from moving? Would I still be able to adjust it with loctite?

If anyone has advice on how to know when to stop screwing the air screw in too, that would be nice. I dont want to overtighten it and break the needle but I wonder if Im not screwing it in tight enough to begin with either. My bike seems to like it about 2 turns out and the screw can sometimes move around when I ride at that position. Thanks  :cheers:
« Last Edit: March 13, 2020, 02:08:27 AM by BikerBoy »

 

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