Is it normal for the return to idle to be this slow?



I'm just putting bike together after a re-jet & rebuild (40, 125, 3 turns, stock exhaust). The bike did the same thing before...I thought the rejet might cure it. I checked to make sure throttle and choke were clacking all the way closed while putting it back together.

Does seem pretty slow.  Mine's like that too but my last GS500 was quicker to return to idle.
Mixture is off.

IIRC you're too lean.  Mix screws need to move... out?  Yeah.

I've got mine jetted just about the same way. Mine did the same thing until i drilled out my slides using a 5/32 bit.

Quote from: Watcher on June 18, 2015, 02:59:23 PM
Does seem pretty slow.  Mine's like that too but my last GS500 was quicker to return to idle.
Mixture is off.

IIRC you're too lean.  Mix screws need to move... out?  Yeah.

Really? Hm. I thought backing further out on the air mix screws would make it leaner. Time to go stare at the exploded carb pic again for another few hours...

I'm confused too. Mine does the same. Can someone please clafiry which way to go on the mix screw?

Edit: My bad, got it backwards... was thinking of my old bike 

Loosening richens mixture.

Quote from: Supa on June 19, 2015, 08:46:58 AM
Backing out leans the mixture. It creates more of a gap allowing more air in. Tightening richens the mixture by allowing less air in. You could also have a small vacuum leak. I recently have been dealing with a leak around my intake boots that made me increase my idle screw and hangs the throttle a bit. It just started to develop, so I'm working through it. I secured the boots better to the intake and that lessened the problem, but I believe the clamp around the boots are worn and stretched causing it to be loose when connected to the carbs. Gonna replace those and see if that finally fixes my leak.

Supra,

You are incorrect unless you have a mixture screw pre carb butterfly. I'm almost positive that all GS500 carb adjustment screws are post butterfly valve hence them being fuel mixture screws not air mixture screws. If you screw them in the outward direction, it lets more fuel into the carb body making it richer. Vis versa the other way.....

 

Quote from: Rallyfan on June 18, 2015, 09:12:04 PM
I'm confused too. Mine does the same. Can someone please clafiry which way to go on the mix screw?

Opening mix screw richens the mix. No doubt about that. The mix screws are a tapered obstruction in an obliquely drilled fuel passage. Take the obstruction out and it puts less of a restriction in the fuel passage. Its not a linear effect either. The difference between 3 turns and 3.5 turns isn't exactly .5/3 X 100 as a percentage ... its more like 1/3 X 100 ... LOL ...

Quote from: Physic55 on June 18, 2015, 04:48:56 PM
I've got mine jetted just about the same way. Mine did the same thing until i drilled out my slides using a 5/32 bit.

What drilling slides - don't do nothing for idle return. It makes the carbs react faster to opening throttle ... except ... the carbs already react far faster than the engine, and usually it makes it suck air and fall on its face when you whack the throttle open. The usual trick has been to close off 1 hole in the slide when doing K&N and pipe, so the slide lifts slower ...

Remember the slides are $$$$$ and I only have a few 89-00 slides sitting around by virtue of killing some katana carbs ... so you destroy a slide on a 01+ ... you may be on your own. I've bailed out a few 89-00's cos I ... well am a pack rat.

Cool.
Buddha.

It's not slow, but it could be a little faster.

Most probable cause imho is carbs out of sync.

On the GS there's a screw in between them to adjust (level) them.

Could be mis-configured, or perhaps a small piece of debris stuck in one jet, causing one cylinder to work harder than the other.

Happens most of the time on a 360 degrees parallel twin cylinder engine.

One of the reasons why I'm going back to single cylinder bikes (like the Honda CB300F).

Yeah, I finally got off my arse and backed out my mix screws.  One full turn out each and reset the idle via the thumb screw and it's a lot better dropping RPMs.

Quote from: Watcher on June 19, 2015, 10:47:05 PM
Yeah, I finally got off my arse and backed out my mix screws.  One full turn out each and reset the idle via the thumb screw and it's a lot better dropping RPMs.

so how many turns are you out now?

IIRC I'm out 4 turns.

40 pilots, 135 mains, stock intake/exhaust, 1 washer on the needles.