Idles at 7k??

[Candyman]

Ok, I'm with you, only thing that makes me doubt is that I didn't see any difference in idle when I sprayed the area with ether.

I was spraying at the back of the boots though, not at the front where the O-rings are. I would think it still would have sucked some in, but I could be wrong, I'll try to spray them again.

[Candyman]

Soaked the things everywhere I could with ether while it was running and no change in the revs, just roaring away at 7k. So I'm not thinking vaccume leak.

Please correct me if I'm wrong on any of these, but from what I can tell in the manual, there are a few things different about the jetting in my carbs.

Stock main jets should be 117, mine have 120's. A common enough mod I gather, to richen up the stock lean settings???

Pilots should be #37.5, mine has #40's

Main air jets (the ones right by the airbox boot) should be 1.7, mine say 155 (1.55?)

Float bowl settings seem dead on.

This sound odd to anyone?

[Nessism]

The problem is not the jetting. You either have an air leak or the throttle plates are jacked up.

[Woodsy]

I was under the impression that even recoed carbies need to have everything set on them, they dont come pre tuned. Have you physically checked the butterfly operation etc with them off the bike?

[Candyman]

Yes, I've checked the throttle plates , off the bike, they function fine. In order for it to idle that high due to the throttle plates they would have to be stuck about half open, which they are not. If anything they might be adjusted a tad bit open, but nowhere near half way.

This is turning into quite a mystery.

[Larry D]

Here's my "guess"......You say you backed the master idle knob all the way out.

Are you sure the plate that the screw controls is not stuck somehow. I'm thinking that you backed the screw out but it didn't do anything to release the butterflys. If the butterflys were closed there is no way it should idle that high, so, the butterflys have to be stuck open somehow.

Are you sure you were turning the screw to close the butterflys and not open them ?

[tom203]

Yes, I've checked the throttle plates , off the bike, they function fine. In order for it to idle that high due to the throttle plates they would have to be stuck about half open, which they are not. If anything they might be adjusted a tad bit open, but nowhere near half way.

This is turning into quite a mystery.

No, with no load on engine (idle), the throttle plates ( maybe just one or all) would only have to be "a tad bit open" to let engine race- combine this with a small intake air leak from boots or o-rings and you can get high revs. Back off your idle stop screw to close throttle plates down- your idle / air circuit should be able to do its thing.

[tejasmud]

Edit: What Tom says. Beat me to it. Lol

It doesn't take much opening of the throttle plates for the idle to be high without load on an engine.

If you can tell they are open with the idle adjuster backed all the way out then they are most likely open too much.

The "choke," enrichening circut, could be subject as well. Is it on or off? Do all the plungers close all the way? And, are the rubber discs of the plungers good? These are some questions that might want to be answered.

If the sync port screws are sealing, the intake spigot flanges/boots are plyable and not cracked, preferably new, the vacuum hose is not leaking, and the o-rings are new then not much left. In opinion it's getting more air through the throttle plates or choke.

E

[Larry D]

Okay......so maybe the bench sync is way off and the butterflys are being left open to far even though the idle knob is closed. A solid carb sync may cure the issue.

[Nessism]

Okay......so maybe the bench sync is way off and the butterflys are being left open to far even though the idle knob is closed. A solid carb sync may cure the issue.

What Larry said plus...

[69chris]

fuel tap seal's shot (if its got a vac tap) feeding fuel straight into carb no 3 ??

[Skateguy50]

From experience I would say start at the beginning again and do the full carb job, and save some time in the long run.

With that said I know my bike will run that high if I left the choke fully open, so if you know the butterfly is closing with idle set back and the throttle cable isnt opening it the only way in my mind for it to stay that high is for the choke (fuel enrichment) to be stuck fully open.

I would investigate that system first.

[Candyman]

To answer a few questions:

Yes, I am sure that the idle adjust screw is completely backing off, allowing the butterflys to close.

Yes, choke plungers are all closing, I suspected that as well at first.

And regarding the minimal throttle plate opening to cause the high idle... I wouldn't have thought it would, but I'm going to go over the carbs again carefully tonight, and make sure the throttle plates are adjusted as per manual and give that a go. I'll take a pic of how they are before I adjust them.

Oh it would be so nice if that cures it...

[SVSooke]

I sold these carbs to Candyman.They are off a 83 GS750ESD.This one:

It was not running when I bought it,there was no exhaust.Didn't try to start it.





They are a good looking set of carbs.I have no idea what's wrong here.

[Candyman]

Much thanks guys, you got me looking and thinking in the right direction at least. Turns out wasn't the carbs at all.

Stupid thing. Always is.

Just for information sake, having your throttle plates open just this much, will make your engine idle at about 7k:



I checked the throttle plates on the bench and they looked perfect, no adjustment needed. Then I checked them with the cable hooked on and the cable adjusted as loose as it would go. I noticed this time that they were open just this little bit. Ok, not bad, a little cable adjustment will fix that right? Well, the cable was as loose as it would go on both ends. Finally thought to take apart the throttle tube assembly at the other end of the cable, and this is what I found:



Cable had jumped the track and was taking up that last 1/8" of slack I needed to close the butterflies completely. Judging by how it was bent I would say it has been like this for a long time, maybe even what caused the previous owner to park it an pull the carbs who knows how many years ago. Maybe a 7k idle was making him think bad carbs too!

Fortunately SVS of my carbs was kind enough to throw in the cables with it (Thanks!) so I just put that one on. Started it up, set the idle, and took it for a little spin up into 4th gear. Could still use a bit of a carb sync but she runs just fine otherwise.

Thanks again for all the help guys, it got me looking in the right direction.
Cheers