Idle is sticking for a bit too long...

[TheDooman92]

So I just put the carbs back in my bike after replacing some lower float bowl gaskets which seemed to fix a slow leak coming from the seem. I reconnected all of the hoses and I am now second guessing the way I did it  here is my current issue: Bike starts just fine, idles around 1500 RPM when warm. When throttling up around 4-5 in neutral, bike does not idle down regularly. The needle sticks around 3000rpm for what seems to be too long. The bike also sputters with some backfire when using throttle and when laying off throttle and letting RPMs settle. Why is my bike sticking at higher idle? Almost sounds like it's running lean. Possible vacuum leak? Not sure how to correctly put the vacuum hoses back if I did do something wrong. Any help would be super appreciated.

Andrew.

[TheDooman92]

Here is a pic of the current hose routing. Something is telling me there's a hose connected in the wrong place. Thanks guys!

[mr72]

Idle is set too high. That's all.

[TheDooman92]

It's idling at around 1400 rpm after 20 minutes warming up (not riding, just idle and some throttle). I am actually worried (don't know if I should be...) about taking it on the road because I don't know how it will act with the RPM delay at around 3-4000RPM before falling slowly. Bike was running just fine before I reinstalled the carb (despite the small carb fuel leak), but a friend of mine did happen to set the idle (by hand using knob below the carbs) higher before the bike was fully warmed because it was falling below 1000 and stalling just after putting the carb back on and getting running. Does this change your diagnosis? How do you suggest that I lower the idle so the bike stays running without applying throttle? Is it just the one knob at the bottom you turn, or do you adjust the mixture screws as well? You don't think there's a potential leak somewhere (manifold boot, vacuum hoses, etc) which is causing the hanging rpm issue? Once again, I'm new to the bike world so any info you can pass on is a huge help and I really appreciate it! Best,

Andrew.

[mr72]

Yes the idle is set too high. The idle mixture might also be wrong.

Set it according to the guide on my blog. You're going to have to ride it it on the road for 20 minutes before you can set the idle mixture. It shouldn't run without choke until it's warmed up.

https://joshkarnes.blogspot.com/2017/09/fixing-common-gs500-carburetor-issues.html?m=1

[TheDooman92]

Thank you for the tips really appreciate I am going to follow your advice. I noticed when the bike is warmed up and I put choke on full the bike will rev to around 8000 which I figured was high. Is that because the idle is set high? Or maybe this is normal?

[mr72]

Seriously, go read my guide on the blog post. It explains all of this.

Bike revving like mad when warm and choke is on is normal.

Bike dying while trying to run without choke when cold is normal.

You know the choke is for cold starting right?

[TheDooman92]

Hey thanks for getting back. Yeah I know the choke is for cold starting, I was just messing around with things after I got the carbs back on. I'll update how it runs after adjustment in the next few days. Thanks for your help. Andrew.

[TheDooman92]

So I followed your advice and it seems like the hanging idle issue has come to a stop. The bike is idling around 1100 RPM, and there doesn't seem to delay anymore coming back to the 1100 RPM idle. However, I've noticed that the bike will not reach redline before I gear up. It seems to hit 9000 RPM and hover there, and not going anywhere higher (10-11000) with increased throttle. Is this normal? Am I missing something here? Did I set the idle adjuster slightly too low?  Thanks kindly! Hope to hear back with your info!

Andrew.

[mr72]

Not revving past 9k is not related to idle mixture or speed.

The power peak is at about 9k. There is really no reason to rev past that and it may not make enough more power to keep accelerating after 9k depending on gear and load. If it won't rev past 9k at wot in first gear then there maybe something causing low power, but that could be many things, none having to do with pilot mixture. Vacuum leak could do this, damaged carb diaphragm, low compression, way too small main jet, low floats, carb vent hose facing forward, bad intake boot o rings, fuel flow restrictions, among other things.

[Meukowi]

have you syncced ur carbs? did mine and throttle response is way better now aswell as idle, idle speed lowered from 1500 to around 800 after sync.

[IdaSuzi]

I haven't had this experience on bikes yet but in my automotive experiences, decent running at idle and low rpm and no high rpm power is often an indication of running lean. Fuel starvation doesn't show till higher in the rpm range at an open throttle. First I would check the spark plug color. If it is showing light or white coloration on the plug, then it could be a vacuum leak, fuel starvation etc. Good luck!

[Kookas]

I haven't had this experience on bikes yet but in my automotive experiences, decent running at idle and low rpm and no high rpm power is often an indication of running lean. Fuel starvation doesn't show till higher in the rpm range at an open throttle. First I would check the spark plug color. If it is showing light or white coloration on the plug, then it could be a vacuum leak, fuel starvation etc. Good luck!

Hanging idle also is a classic lean symptom. I don't think the bike should rev that high on full choke either (mine doesn't come anywhere close to 8k) so I think it's probably running lean because of excess air rather than lack of fuel?

[mr72]

Hanging idle also is a classic lean symptom.

Well it's a classic misdiagnosis as lean idle, or a classic side effect of trying to fix lean ide. It's classic to set the idle too fast to compensate for lean idle mixture, then wind up with hanging idle. But the hanging idle is caused by the idle being set too fast. Idle speed can't be set independently from idle mixture. The carb is intended to idle with the throttle plate closed completely. Opening the throttle plate at all at idle will absolutely result in a lean idle. If it idles too low with the throttle plate closed then the idle mixture is wacked and needs to be fixed.

I don't think the bike should rev that high on full choke either (mine doesn't come anywhere close to 8k) so I think it's probably running lean because of excess air rather than lack of fuel?

I thought the OP was talking about revving to 8K on choke when the bike is warmed up, which is normal.

It will never rev too high because it's lean, no matter what. You don't get more running with less fuel. But you are kind of onto something about "excess air", because excess air across the main jet will result in more fuel as well and make it rev too high... which is exactly what's happening with hanging idle, if you open the throttle plate too much with the throttle stop (aka "idle speed knob"), then you allow too much air over the main jet which results in too much fuel and air and keeps the idle "high" until such time as the vacuum reduces enough to drop the slide all the way into the main jet. This is hanging idle. You could shim the needle to force the main jet to stay partly open in this condition and then you'd just wind up with a consistently too-fast, hunting idle, because cracking the throttle a tiny bit is a very poor way to meter air.