Idles at 7k??

[Candyman]

Just got a set of carbs for my project bike, they had been sitting a while, but I wanted to try them out right away so I did. My bikes fuel tank is rusted so I had to rig on a tank from from another bike I have.

Despite a bit of gunk I still got it to start, but it idled at about 7k. I killed it, thought it might be the throttle cable too tight. So I tinkered with the throttle cable adjustment at the carb end, tapped the carbs to unstick any slides that might be sticking, tried again and it idled perfectly. So I pulled them an gave them a 24hr Pinesol soak.

Now, I reassembled them tonight and fired it up again. Started great this time, but it idled at 7k again. It would rev higher if I twisted throttle, but it would NOT idle lower than 7k.
Things I tried:
Backed off idle screw all the way.

Adjusted cable adjusters on throttle cable at carbs all the way loose.

Took the cable completely out of its notch on the carbs so the cable was hanging free.

Disconnected choke cable to make sure it wasn't staying open.

Tapped carb boddies repeatedly to try to free up a slide that might be sticking open.


I'm at a loss here. Suggestions anyone?

 

[Nessism]

Dude, you haven't done any research at all yet. Rebuild the carbs right. There are about a billion posts in the archives stressing the importance of clean carbs with fresh O-rings. Carb rebuild information is on the GSR homepage. Get O-ring kit from cycleorings.com and don't forget the intake boot O-rings if your bike has them. Short cuts are long cuts.

 

[Steve]

There are also different suggestions on what to try based on what type of carbs you have.

We have no idea what carbs you are talking about, we also have no idea what BIKE you are talking about.

And, Nessism has it rather correct, you can't just take a set of carbs that you admit "had been sitting a while" and expect them to work.
Actually, it's rather amazing that they woked at all.
Congratulate yourself on finding a set of dirty carbs that would actually allow the bike to start. :clap: :clap:

Now, when your hands stop banging together, take those carbs apart and clean them PROPERLY. There is information in the Garage section of the GSR home page, that same information is linked in BassCliff's site, which should be rather easy to find, because you have it bookmarked, right? :-k

.

 

[blowerbike]

has anyone ever covered carb rebuilds on this site

 

[Adler]

has anyone ever covered carb rebuilds on this site

Nah, I dont think so... Maybe someone should do a detailed writeup and put it on BassCliffs site...

 

[blowerbike]

Nah, I dont think so... Maybe someone should do a detailed writeup and put it on BassCliffs site...

now that i think about...
maybe do a write up on valve shim adjustments...yeah..put that on basscliff's site also.

 

[Adler]

You don't even have to go to Basscliffs site, the tutorial is on the GSR homepage.

Unless you happen to need the VM guide....
The point is the same... Pretty much ALL the info is readily accessible.

 

[Candyman]

The bike is an 84 GS750E. And thanks (yet again) for the point to BassCliffes site. Been making good use of it.

Thanks, but not really helpful info guys. What would be helpful would be to know if there is any history of a carb demonstrating symptoms like this and it being solved immediatley via a new O-ring kit? Or maybe a suggestion as to what O-ring might be bad, causing this to happen?

The O-rings I saw while disassembling these carbs were in better shape than other bikes I have seen, so I opted to not do an O-ring kit right now. I've had carbs with painly cracked and rotten O-rings when I tore into them, but they still ran before I pulled the carbs, just would not run well. None of them ever gave me symptoms like this though.

 

[Nessism]

The bike is an 84 GS750E. And thanks (yet again) for the point to BassCliffes site. Been making good use of it.

Thanks, but not really helpful info guys. What would be helpful would be to know if there is any history of a carb demonstrating symptoms like this and it being solved immediatley via a new O-ring kit? Or maybe a suggestion as to what O-ring might be bad, causing this to happen?

The O-rings I saw while disassembling these carbs were in better shape than other bikes I have seen, so I opted to not do an O-ring kit right now. I've had carbs with painly cracked and rotten O-rings when I tore into them, but they still ran before I pulled the carbs, just would not run well. None of them ever gave me symptoms like this though.

Did you change the intake boot O-rings? This a VERY common issues - the O-rings are almost certain to leak if they are original. Bad O-rings allow false air to entire the engine, leading to a high idle. That said, I've never seen an intake leak cause a bike to run at 7000 rpm so you might have a couple of issues combining.

 

[Adler]

Is it a steady 7k?

 

[Candyman]

Did you change the intake boot O-rings? This a VERY common issues - the O-rings are almost certain to leak if they are original. Bad O-rings allow false air to entire the engine, leading to a high idle. That said, I've never seen an intake leak cause a bike to run at 7000 rpm so you might have a couple of issues combining.

No, I did not change any O-rings, though I'm unclear on which you mean by "intake boot O-rings". Please help me out with which you mean so I can examine them.
---EDIT: Are you just meaning the intake boots themselves? Or is their an O-ring between the boots and the engine that you are talking about? I quick shot of ether around there would show a leak I suppose.

Thanks for the help.

@ Alder: Yes, a very steady 7k(ish). It will climb fine when I rev it, then drop back down right to the same 7k area to idle.

 

[Candyman]

Anyone know off-hand what should the idle screws be set at on these carbs? 3.5 turns out?? (I don't have my manual on this computer) May as well check them too.

 

[Adler]

Sounds very much like a stuck slide to me, but I do not have CV carbs so I'm really just guessing.

 

[Candyman]

Thats what my initial thought was too, but like I said, before I put the carbs on it pushed the slides up and they all slid back fine. ???

I just went and tightened the clamps on the intake boots as tight as I could, I started it, and this time it hovered at 3k, then 4k, then climbed back to 7k. Gave another quick tighten check and started again, and right back to 7k again.

I gave a close look to the intake boots and there did look like some cracking around where the cylindrical part meets the flange. So I started it again -it went straight to 7k- and sprayed some ether at each of the intake boots, and there was no change in idle at all.

hmm.

 

[GSX550]

The intake boot o-rings everyone is talking about are the o-rings that seal the connection between the boots and the engine. With the carbs removed you should have the boots left connected to the engine. Each of these boots is held on by two likely stuck phillips head screws. To get them out get a good fitting screw driver and give it a big whack and apply mountains of pressure towards the engine then twist. When they come off you will see the o-ring that we are talking about. Replace these! And replace the phillips head screws with socket head screws (Allen head, etc).

Then see how you go.

 

[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.