GS500 Idle Issue

I

icebox

Member
Hey all, have a new and exciting issue with my GS500. It's an '08 model, with about 14k miles on it. It's run like a dream through regular maintenance and routine riding. Yesterday, my wife and I were out for a short ride and I noticed about 4 miles down the road at a stoplight that my bike was idling low, at about 1100-1200 rpm. (Normally after a warm up it's about 1300-1400). After another 5 miles and at another stoplight, it slowly, ever so slowly, died out. I started it up (taking a little more throttle than I normally give it) and drove back to my house. If I had to stop, I had to give it gas to keep it running. When I got home, I checked the usual stuff.. Airflow, fuel, petcock. All were fine. Switching to reserve or PRI didn't do anything to make it stop.

So I let it cool down completely overnight, and went out this morning to see what I could figure out. Turned the choke on, about half way as always, started it... Starts like I've always started it. A few seconds later I take the choke off, and it idles fine. Low, but normal because the engine was cool. So I let it warm up idling. And it does, returning to it's normal idle of about 1400. After it hits this mark, I took it for a ride. Runs fine, for about 5 miles. And the problem returns. It just slowly dies out from idle, almost like it's starved for fuel. But I can twist the throttle and it jumps to life. Don't know what to look at.. I never let it sit for more than 3-4 days without riding.. Oil is good, all factory tuning and exhaust.

Any ideas?
 
Check your gas tank vent to make sure it's not clogged which can cause a vacuum leading to a fuel starvation problem. Also check your gas cap vent as well (if the GS has one) as it may also be clogged.

500R's and even some of the 250's are known to have this issue with the gas cap. They have two one-way valves (little orange rubber disks) inside the gas cap. The first valve is usually the problem. It dries and hardens which can seal the opening and also cause a vacuum in the tank causing similar starvation problems.
 
My runs around 1200 rpm when it warms up .

Was told it by the dealer thats its normal to run between 11 and 12 rpm
 
Over the winter take apart and clean your carbs.
 
Have you tried to turn the idle up? The temp has changed by quite a bit outside....
 
I'll check the gas vent this morning (I should just be able to pop open the fill cap and see if there is a difference, correct?) The only thing that's bothering me is it only does it when it's warmed up completely, and only when it's been returned to idle. I really don't feel it's the best course of action to up the idle, especially if it's stalling out from 1400 rpm. If it went directly to a much lower rpm after letting off the throttle, and held there I'd be happy turning it to adjust.
 
Sabex said:
Over the winter take apart and clean your carbs.
Click to expand...

+1

Add a fuel filter to prevent problems in the future. Also, check your idle speed it seems high. Again, I don't have a GS but the idle on my bike is ~1200rpm.


Sent from my iPhone
 
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Will do. Is a carb cleaning necessary over the winter if I still ride as often as I do in the summer? I agree, the idle does seem a little high. I'll tweak that once it's warmed up and idling on it's own properly. Good idea on the fuel filter as well.
 
A carb cleaning is not required for storage purposes. It is only required if you are having issues with your carbs (i.e. clogged jets). Generally if you have a fuel filter installed, maintain your bike and properly drain your carbs prior to long term storage you should never need to clean your carbs.


Sent from my iPhone
 
icebox said:
Will do. Is a carb cleaning necessary over the winter if I still ride as often as I do in the summer? I agree, the idle does seem a little high. I'll tweak that once it's warmed up and idling on it's own properly. Good idea on the fuel filter as well.
Click to expand...

As 00ninja said, a carb cleaning is required if you have a carb problem.
It doesn't hurt to clean them out anyways, and also rejet (GS500 come fairly lean from factory.)
 
Ok, I appreciate you guys helping with this one. So I opened my gas cap, and let it warm up, only to find it still dies out slowly at idle. And then I recalled that when the bike was initially giving me the problem, I was riding it for a while below 30 mph. This gave me the idea that maybe the bike was not receiving enough airflow (being only air-cooled) to keep the correct fuel/air ratio in the cylinders for combustion. So I took it out on the highway at 55+ speeds for a good 15 minutes, then I pulled over, and waited for the idle drop. It took about 5-6 minutes to reproduce the issue. It just seems to me that heat is building up affecting something. I can't recall having this issue in the hottest parts of the summer, and I've had to sit at some red lights for quite a few minutes at times or for multiple light changes without it ever stalling during 90-95 degree temperatures.

Any more thoughts? On the re-jetting idea, is there kit that would allow this and would it require a different exhaust setup? I'm not necessarily looking for a performance boost as I am looking to finding the root of this issue.

Thanks again guys!
 
icebox said:
Ok, I appreciate you guys helping with this one. So I opened my gas cap, and let it warm up, only to find it still dies out slowly at idle. And then I recalled that when the bike was initially giving me the problem, I was riding it for a while below 30 mph. This gave me the idea that maybe the bike was not receiving enough airflow (being only air-cooled) to keep the correct fuel/air ratio in the cylinders for combustion. So I took it out on the highway at 55+ speeds for a good 15 minutes, then I pulled over, and waited for the idle drop. It took about 5-6 minutes to reproduce the issue. It just seems to me that heat is building up affecting something. I can't recall having this issue in the hottest parts of the summer, and I've had to sit at some red lights for quite a few minutes at times or for multiple light changes without it ever stalling during 90-95 degree temperatures.

Any more thoughts? On the re-jetting idea, is there kit that would allow this and would it require a different exhaust setup? I'm not necessarily looking for a performance boost as I am looking to finding the root of this issue.

Thanks again guys!
Click to expand...

I would think it's more likely that you have a clogged pilot jet if its happening in the lower end of the rev range.

Jetting.. the way I did it was research which jet sizing I'd need for my exhaust/air filter combo at our altitude. It worked pretty well. Tons of info is availabe on gstwins and the gstwins wiki


Sent from my SGH-I747M using Tapatalk 2
 
GSTwins yes, rejet no. At least for now. Fooling around with the jets only adds another variable to the problem which isn't solved. They're jetted lean to meet emissions standards, but that really only affects warmup times, not useability. My old GS took forever to warm up (PO debaffled the muffler) but ran fine. I did adjust the idle screw up a bit, nothing dramatic.

Grab the toolbox. Airfilter (mice and seeds around now), battery (it could be getting old), sparkplugs (old/fouled from lousy running). Easy to check off that list of suspects. Then bend the ears over at GStwins if it doesn't pan out. The 2008 model is air/oil cooled. Suzuki added the oil cooler when they added the fairing in 2004/2005.
 
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Doesn't sound like a jetting issue so I'd say leave the jets alone but a carb cleaning never hurts.

Even if your running a fuel filter and air filter with fresh gas the odd bit of debries will get by somehow and it doesn't take much to clog pilot jets or pilot air jets. The GS500 carbs are super easy to remove and clean too so you might as well just go for it.
 
I had this issue when I'd go from highway speeds to city speeds, it was like the bike got used to having gas and then couldn't idle properly once the clutch was pulled in so I'd have to rev it through downshifts.

I didn't find that messing with the idle knob helped but I did put a can of seafoam through the gas tank and that seemed to help reduce the amount the issue was occurring, lending credence to the jet suggestion if it was the same thing. Bike got t-boned before I could ever figure out the problem.
 
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