Idles at 7k??

[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

 

[SVSooke]

It's always the silly things that bite you!Seemed like a good idea to send them so thank you.

 

[Larry D]

Good job. A little investigation goes a long way.

 

[Candyman]

Ya, you can never be too thorough.

I got to thinking, and when this all started, I tried running it with the cable completely out of its holder on the carbs. That should have solved the problem, allowing the throttle plates to close. But I must have still had the idle screw screwed in at that point though, so it was still keeping the plates open. Ah well.

 

[etpetnel]

Hah !!!

Hah !!!

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

Thanks candyman, I believe in learning from others' experiences, and I was having a similar problem after I have just rebuilt my carbs, fitted new carb boots, orings included, as well as new orings to the carb. I couldn't understand why the bike was idling so high. I hadn't yet put the airbox and all the pipes back on, so thought that when I vacuum synch the carbs with everything in place she may come right on the high idling.

But it still bothered me, and when I read this thread, I thought to have a look at my throttle tube. Well, I recently put a "new" 2nd hand tube on, and the one I found was for a twin cable carb. So what had happened is that I put the throttle cable in the wrong slot. I just moved it to the other slot, and could immediately see more play in the cable at the carb. Started her afterwards, and idling much lower. Now just have to vacuum synch, and hopefully all my carb issues will be history for a long time to come...

That's why I love this forum....thanks again. Etienne.

 

[BigD_83]

And thank you, Candyman and everyone else who has contributed to this thread.

You all helped me solve a similar problem with my 650. I knew the cable tension was too high, but I hadn't thought to pull the throttle tube off until I saw your pics.