Overheating causes high idle, normal?

[tudorv]

Hi! I'm back seeking more advice from you guys. PLease help me out if you can.

My GZ runs fine now. No real issues with it and I keep putting miles on it. There's just one thing bothering me. After riding for a while (so the engine is all warmed up) if I get stuck in heavy city traffic, in full sun, with sitting cars all around me, after a few go-stop-go-stop routines, the idle gradually increases up to a pretty high rpm. And then it stays like that. (unless i fiddle with the idle screw)
After I get away from the traffic jam and give the engine a chance to cool down, the idle returns to normal.

Should this be happening? If the engine overheats, and the rpm increases, won't that make it overheat even more?

What do you think I should do?

Thanks!

[jonathan180iq]

when you turn your handlebars all the way to the left of right with the bike running, does the idle fluctuate at all?

[tudorv]

It doesn't. It's not the throttle cable being too short or anything. It's definitely related to the engine temperature. Or perhaps the carb becomes somewhat hot and that affects the mixture. But i don't know if this is supposed to happen..

[jonathan180iq]

It doesn't really make sense unless there is a slight air leak somewhere that it only really exposed when everything gets really hot and supple... (that's what she said)

Mixture won't mechanically change with heat unless something is getting hot enough to either:
-Let in more air
or
-loosen up your throttle return spring, effectively leaving your butterfly valve open slightly...

that was all just speculation. to make sure you have a solid starting point, you need to set your idle to a solid state after the bike gets good and warmed up, after that, you shouldn't have to change it.

Can you get the bike to replicate this behavior without being in traffic? If you can do it in your own driveway, then hop off and see if you can see anything physically move. If so, correct it. If not, then give it the ol' WD40-poorman's vacuum leak test to see if something is happening when the rubber gets really hot... I'm kind of at a loss too, so I'm just brainstorming.

[raul10141964]

my do the same setting the pilot screw to 2 3/4 turns solve it

[tudorv]

Thanks Raul! I suspected something was off with my pilot screw. I was afraid to mess with it so I wouldn't make it even worse.

[blaine]

Originally Posted by tudorv

Thanks Raul! I suspected something was off with my pilot screw. I was afraid to mess with it so I wouldn't make it even worse.

That is a good starting point (2 1/4) do fine adjustment with the bike idling warm.When the pilot screw is set properly your idle will sound much deeper & not fluctuate.
:cool:

[alantf]

Just a thought...You do realise that these bikes idle at a "high" revs! When hot (really hot), this is the time to set the big white knob to 1200 to 1400 RPM. When you set off with cold/cool engine, the idle is much slower. When the engine gets hot, the idle rises to whatever you set it to, then slows down when the engine cools. That's just the nature of the beast. Could this be happening to you, and making you think that the "normal" idle of 1200 to 1400 is too high?

[Havoc]

I do believe that's normal. I live in Michigan where its generally cooler. I have to let my gz warm up for a good 5 minutes on full choke before she idols normal. Then the hotter it gets the higher the idol. I just adjust the idol knob once it
gets hot.

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[jonathan180iq]

Idle should be something that you set once, once your bike gets up to temp, and then you shouldn't have to fiddle with it after that.

There is no reason to let the bike warm up while idling in the driveway. That's actually counter productive.
Start the bike with the choke, and take off as soon as she is ready. She will warm up faster and flow oil better by getting her tires spinning. Turn off the choke as soon as you can once you're on the road.