Idle problems

[jevhid]

Hello everyone!
I am a new owner of 2008 GS500 here, and not very familiar with all aspects, so that's why I'm here. It just has 23k km on it. Overall condition is fine. Since I bought it and don't have much money to go to a service, I've decided to do it on my own.

When I just got it it was running fine but I had to use choke for quite a while, otherwise mc was stalling on trafic lights. Therefore, I've decided to try fixing it. What has been done:
-valve clearances checked and shims changed, so it's in spec
-carburetor removed, taken apart (this screws omg), cleaned (looked very clean, just sprayed the jets)
-carbs synced (I used two bottles device). Actually not sure, if it was done quite well
-air mixture screws 3 turns out
-spark plugs changed
-fuel hoses changed (cause one got ripped 3 times while trying to remove it)

So now everything runs fine, but I get some weird behaviour, while idling cold. I start on full choke, keep it while getting ready for a ride, and then lower it to 1.5-2k rpm, while riding it for few kilometers. Then I remove it and everything seems fine. BUT!
It may still stall on a traffic light, and sometimes, I can hear like weird sound from one cylinder (I think one, maybe right), like it drops (misfire? I'm not sure how to describe it precisely). If I drive for long time it keeps idling without any problems. Fx today I stopped for 10 mins, so engine couldn't cool down that fast, and I started it, and it died when I stopped to exit the parking.

Does anyone have a clue what can it be, and what I should look for?

I think the problem should be in carbs, but I also may be wrong. Because I started getting this behaviour after a was working on carbs.

Thanks in advance!

[Kilted1]

Welcome!  First off, these bikes take a long time to warm up.  20 minutes minimum riding on the road before you can say it's fully warm. 

How's your air filter?  Time for cleaning or replacement?

What did the old plugs look like?  What do the new plugs look like since you've done the rest of everything?

Poorly synced is better than not at all synced, but how far out were they to start with?  Did you have to adjust it much?  Would it be possible to have another go with better tools/method?

+1 on doing the valves! 

3 turns on the pilot screws.  Based on what?  Did you just set them there figuring that would be about right?  Or is that where they ended up after tuning?  If after tuning, was it fully warmed up from a good long ride?

After a few kilometers of riding, it should idle reasonably but may still need some choke. 

It's ten years old and it's not unreasonable to think that the O-rings inside the carburetor may be leaking.  The only cure for that is to replace them.  IF that's the case, you can try to tune your way around it but you'll spend less time and aggravation in just ordering the parts and doing the job.  The worst case scenario is that you still have some minor issue but you will know the carbs are tight because you made them that way.  Mr72 has a great blog post on the subject.  https://joshkarnes.blogspot.com/2017/09/fixing-common-gs500-carburetor-issues.html?view=mosaic

[mr72]

Sounds like normal operation to me. You probably just need to keep a little choke on for longer until it's fully warmed up. If you have the stock pilot jets then 3 turns out might be in the ballpark but with #40s it may be too rich, so do yourself a favor and set the idle speed and mixture correctly (with the bike FULLY warmed up) to rule this out.

[jevhid]

Welcome!  First off, these bikes take a long time to warm up.  20 minutes minimum riding on the road before you can say it's fully warm. 

How's your air filter?  Time for cleaning or replacement?

What did the old plugs look like?  What do the new plugs look like since you've done the rest of everything?

Poorly synced is better than not at all synced, but how far out were they to start with?  Did you have to adjust it much?  Would it be possible to have another go with better tools/method?

+1 on doing the valves! 

3 turns on the pilot screws.  Based on what?  Did you just set them there figuring that would be about right?  Or is that where they ended up after tuning?  If after tuning, was it fully warmed up from a good long ride?

After a few kilometers of riding, it should idle reasonably but may still need some choke. 

It's ten years old and it's not unreasonable to think that the O-rings inside the carburetor may be leaking.  The only cure for that is to replace them.  IF that's the case, you can try to tune your way around it but you'll spend less time and aggravation in just ordering the parts and doing the job.  The worst case scenario is that you still have some minor issue but you will know the carbs are tight because you made them that way.  Mr72 has a great blog post on the subject.  https://joshkarnes.blogspot.com/2017/09/fixing-common-gs500-carburetor-issues.html?view=mosaic

Forgot to mention, that I replaced air filter.

Old plugs looked brownish. I didn't put many km on new ones, but when I was taking them out after some km, they were white. Maybe need to check it again. It was like the middle one on the pic, on of the plugs was a bit darker though. Now they look like left on a pic.


I wouldn't say that I had to adjust carbs by a lot, just a bit.

When I first removed the carbs, I decided to check how the screws are. One of them was 3 turns out, another - 3.5. I think that's why there was a difference seen on plugs.

What o-rings are you talking about?

Right now I can see, that the bike is idling worse compared to how it was idling before. It's still ridable but it's very annoying.

Sounds like normal operation to me. You probably just need to keep a little choke on for longer until it's fully warmed up. If you have the stock pilot jets then 3 turns out might be in the ballpark but with #40s it may be too rich, so do yourself a favor and set the idle speed and mixture correctly (with the bike FULLY warmed up) to rule this out.

Jets are 17.5/60/130. What do you mean by #40s?

[mr72]

Ah, I meant the 2-circuit carbs. 3 turns out is probably about right on your carbs but there's no substitute for doing it right. Bad o-rings on those pilot needles will make it basically impossible to set the idle mixture.

[user11235813]

Poorly synced is better than not at all synced, but how far out were they to start with?  Did you have to adjust it much?  Would it be possible to have another go with better tools/method?

You certainly don't need 'better tools' to do a carb sync what's wrong with the two bottle home made tool?

The levels in the two bottles does not have to be the same, they just have to not move relative to each other.

[jevhid]

Well, was riding my bike for all this time, still randomly happens. I found a video with the same problem: https://www.youtube.com/watch?v=HsxBpwPuQRc

Can anyone point out a possible cause to it? It's about time to put my bike in a storage, so I will have a lot of time during winter to play with my carbs.

[TGTwin]

Mine did that sound for a long time (sounds like a miss at idle) and these are the things I have done which (touch wood) has settled it.
1. Make sure the "idle speed" screw isn't making the idle too high, or just screwed out too much compensating for other issues. I found a bad carb can be made to "idle" by just messing with this speed screw, but then you see the miss problem.
2. Check no air leaks in intake boots/vacuum lines
3. Make sure carbs are clean/no bad o-rings
4. Make sure carbs are synced.
5. Make sure floats are set correctly.
6. Make sure cylinder compression is good (good rings, valves not tight)
7. Set the pilot screw properly ( https://joshkarnes.blogspot.com/2017/09/fixing-common-gs500-carburetor-issues.html?m=1 )

In all my trials I only just recently tested and fixed my float bowl height, and my idle finally feels a lot better. I reckon if you can definitively do all of the above you should be able to fix it.

[user11235813]

Unlikely to be compression or valves. My bike run fine at 115psi and 120psi. So don't let that fool you. It's almost definitely just the carbs. Either internals or air leaks. Might be worth a professional carb rebuild. But before you go there you should do *all* the o rings that you can get to. You need to track it down till it's all good otherwise it will just keep being a problem.

[Kilted1]

Poorly synced is better than not at all synced, but how far out were they to start with?  Did you have to adjust it much?  Would it be possible to have another go with better tools/method?

You certainly don't need 'better tools' to do a carb sync what's wrong with the two bottle home made tool?

The levels in the two bottles does not have to be the same, they just have to not move relative to each other.

Only because the OP was questioning how well it was done.  Nothing at all wrong with the bottle method.  That's how I do them. 

[TGTwin]

Unlikely to be compression or valves

I only mention it because at one point I did a carb clean and valve shim change, and afterwards my idle was horrendous. I thought I'd messed up the carb but I couldn't fix it by fiddling with the carb. It ended up being the new exhaust valve shims being wrong (no gap, always tight) which would have held them open at least a little all the time. I fixed the shim problem and immediately my idle improved.

[mr72]

Well, was riding my bike for all this time, still randomly happens. I found a video with the same problem: https://www.youtube.com/watch?v=HsxBpwPuQRc

Can anyone point out a possible cause to it? It's about time to put my bike in a storage, so I will have a lot of time during winter to play with my carbs.

If I had to guess, I'd say your "idle speed screw" is set too high, and you have one or more vacuum leaks and/or clogged passages in the carbs.

Sounds like you've tried to make it idle on the main jet and periodically vacuum falls low enough to let the slide drop and it does this.

Just guessing. The fix is the same either way. Rule the carbs out entirely by doing the job right. Make absolutely sure you don't spray carb cleaner on the assembled carbs and do not trust the idle mixture settings until you have adjusted it with the bike completely warmed up after like 20 minutes of riding it on the road.

Could also be an intermittent ignition coil failure, but carbs are much more likely so start there IMHO.

[jevhid]

Unlikely to be compression or valves

I only mention it because at one point I did a carb clean and valve shim change, and afterwards my idle was horrendous. I thought I'd messed up the carb but I couldn't fix it by fiddling with the carb. It ended up being the new exhaust valve shims being wrong (no gap, always tight) which would have held them open at least a little all the time. I fixed the shim problem and immediately my idle improved.

No, I'm totally sure about valve clearance because I double checked it. I will try to follow the suggestions posted above and fix it.