Fast Idle Issue

[Rudi]

Friends,
I can't seem to find a thread to help me with a particularly irritating problem. I finally got my new (to me) 1980 550 up and running...yesterday she was idling perfectly at about 1200, today she is at 4k and the idle adjustment screw is spinning freely with no effect. Two questions:
1) If my idle adjustment screw (brass bugger up-side-down in the middle of the carbs) is spinning freely without bottoming out or coming loose, what does that mean? (Is it stripped out, is it mechanically limited, etc?)
2) How would you begin trouble shooting the problem?
I'm the worst possible combination of a newbie and not terribly bright so bonus points to anyone who can offer advice that is accessible to a fruit fly with ADD (that would be me.)
Regards,

Rudi

 

[Calvin Blackmore]

id say yer throttle cable is hung up somewhere
holding the throttle open and preventing the bit that is moved by the idle adjuster form getting within range

 

[Rudi]

Sounds like a fair place to start...I'll look into it. Any ideas about why the idle adjustment screw is wonky?

 

[Calvin Blackmore]

Sounds like a fair place to start...I'll look into it. Any ideas about why the idle adjustment screw is wonky?

you mean freely spining ?

it should have a spring to keep tension on it
I have not seen one that didnt

 

[Rudi]

you mean freely spining ?

it should have a spring to keep tension on it
I have not seen one that didnt

Unfortunately, it looks like I may have a first (that is, an adjustment screw without a spring.) On the bright side, that may well explain the problem. It looks to me like the throttle cable is alright. Dr. Blackmore, I hope you have a long and happy life...thanks for the help.

 

[Nessism]

Intake boot O-ring leaking.

 

[Rudi]

Intake boot O-ring leaking.

Nessism,
Hmm...This sounds pleasantly manageable. So let me display my ignorance. I've found what appears to be the air intake under my seat (as it were). I get the strange feeling that this isn't what we're talking about though because a leak here would hardly be a problem. I'm guessing the intake boot-a-ma-bob is in the carburetor itself. Using little words (aware that I am both dense and without a manual at present) how should I go about evaluating this? Any guidance would be most appreciated.

 

[Ohioan]

intake boot = rubber thingy between carbs and the engine. Unscrew those, and there is an o-ring there. Replace boots and o-ring.

www.cycleorings.com is your source for those o-rings.

 

[Rudi]

Uh...Did I kill something?

Uh...Did I kill something?

So...I decided to replace chain and sprocket first because that seemed more manageable and it had to be done. I've got the drive train sorted, so I thought I'd fire things up to see how they run. As soon as it fired it began pouring gas out of the rubber hose that is apparently coming out of the mysterious intake boot.
Does this confirm the previous diagnoses or have I managed to destroy my bike before I even got started? Any advice would be most welcome - just note that I have a wee little brain so short words and simple explanations are best.

 

[Nessism]

Any advice would be most welcome - just note that I have a wee little brain so short words and simple explanations are best.

What maintenance have you done?

 

[Rudi]

Ah...

Ah...

That's the strange part, this is new behavior, but so far all I've done is:
1) Replace the battery
2) Replace the sprockets (cover, etc. are still off, but do not seem to be connected to the problem.)
3) Replace the chain
4) Replace the air filter with an OEM filter that came with the bike

I did hook up a carb tuner to the little ports nibblets, but all appeared to be fairly well balanced.

Please feel free to let me know if this is simply a waste of your time - at some point here, I think I'm going to have to start at the gas tank and the air intake and walk through the whole system just making sure that hoses, the petcock, o-rings, carbs, etc are all functioning.

Thanks for the interest.

 

[Nessism]

Please feel free to let me know if this is simply a waste of your time - at some point here, I think I'm going to have to start at the gas tank and the air intake and walk through the whole system just making sure that hoses, the petcock, o-rings, carbs, etc are all functioning.

Thanks for the interest.

No GS bike leaves my garage until it's had all this stuff done. Until you do all the basic maintenance you never know when the bike will break down next.

 

[mike_of_bbg]

I did hook up a carb tuner to the little ports nibblets, but all appeared to be fairly well balanced.

Did you get those sealing screws back tightened in pretty well? Leaking air through those will easily get you to 4k. Ask me how I know

 

[Rudi]

The Forum Helps Again

The Forum Helps Again

Friends,
A couple of thoughts. First, my problem appears to be identical to the problem on this thread Looks like I'm getting ready to replace some o-rings and check out the floats.
Second Mighty Mike of BBG (Please tell me that's the Brooklyn Botanic Garden) - I'm definitely going to look at tightening things up a bit.
Just for the sake of clarity, I am a COMPLETE moron when it comes to all things fuel related and I am scared spitless that I will destroy the old girl when I try to fix her carbs...Rest today, work tomorrow, destroy my bike on Tuesday. At least I'll have a good group to come crying to when she's in pieces on the floor and I'm utterly lost.
Regards and thanks for all the good guidance.

Rudi

 

[Steve]

Sounds like you are in need of some experienced eyes. :-\\\

In which corner of oHIo are you hiding? :-k

There's a BUNCH of us down in the bottom-left corner, just give a holler.

.

 

[mike_of_bbg]

Second Mighty Mike of BBG (Please tell me that's the Brooklyn Botanic Garden)

Not mighty here - I'm about as noob as you are And no, the bbg is from my current home town of Blacksburg. Nothing Botanic. Some people have green thumbs, some brown: I have a black thumb. I look at plants and they die. That is, if I want them to grow. If I don't then they'll grow like weeds (which they probably are).

As soon as it fired it began pouring gas out of the rubber hose that is apparently coming out of the mysterious intake boot.

Let's get this straight first.

There are two hoses which connect to the petcock: a fuel hose (duh), and a smaller-diameter vacuum hose which connects to a tap on carb #2. The vacuum from carb #2 goes through this hose and pulls a diaphragm which allows fuel to flow when your petcock is in the ON or RES positions. THERE SHOULD NOT BE FUEL IN THE VACUUM HOSE! If there is fuel in the vacuum hose, then that diaphragm probably has a tear in it, and the whole petcock should be replaced (very limited reports of success on rebuilds). Since your bike is an 80, it probably has that oddball petcock with no PRI position (which would allow fuel to flow without the vacuum).

Also, if you disconnect the vacuum line, you must plug the tap on carb #2 (or plug the hose if you left it in the carb and unplugged the petcock end).

High idle is caused by too much air getting through (or around) the carbs. If your intake boot o-rings are original, then it's likely they need to be replaced, and they can definitely leak some air. But I kinda doubt that they suddenly went from stable 1200 RPM to 4k RPM. So, some things to check:

1. Is your petcock vacuum tap on carb #2 open? If so, carb #2 can suck air through it, bypassing the throttle.

2. Did you replace the plugs on the intake boots after doing the carb sync? To do the sync the plugs come out and taps go in: to which hoses for the carb sync gauge are connected. Those taps allow air in (which I mentioned before). Make sure the plugs went back in and are snug.

3. Is the choke operating freely? The so-called "choke" on these Mikuni carbs is actually a fuel enrichment circuit which allows an enriched fuel AND AIR mixture through the carbs. 4k RPM is not unlikely with choke stuck open.

4. Did you adjust any of the screws when you did your carb sync? The point of the sync is to adjust the relative opening of the throttle plates on each carb (eventually all relative to #3, the master carb on 4-cyl GSes). If one or more carbs are closed too much, that can cause the others to hang open and let too much air in.

5. Sticking throttle cable? There should be about 1 mm of slack in the throttle cable.

When you replaced the air filter, did you just replace the foam element? Did you oil it? Is it back in tightly?

 

[Rudi]

Mike,
First, you lucky thus-and-such. I went to college about an hour north of you in Harrisonburg. The 81 corridor has got to be one of the most beautiful places on earth. Regarding your "noob" status, I'm afraid I was unclear. I'm both a noobie and hopelessly incompetent - see the difference? Thanks for the clear talk through. Point by point,
1) Vacuum tube seems to be on the straight and narrow - dry as minister.
2) I'll be rechecking the plugs after supper...
3) Choke appeared to be free, but I'll give 'er another peek.
4) My bike started yarfing fuel through the tube feller (see post from 07-02-2010 05:06 PM) so I haven't gotten around to syncing the carbs.
5) I'll be checking the throttle cable.
Thanks for all the suggestions, we'll see what happens next.

Steve,
I'm afraid I'm a bit more toppish on the left hand side. Just a smidgen north of Lima. Also, I have a high concentration of ignorance, so I'd be a bit concerned that the dumb might rub off on a visiting expert. (Osmotic pressure and what-not...8th grade science wasn't my strong suit.) All the same, if there is someone roughly in the area and you're up for the live comedy of me with tools, stop in and I'll be glad to feed you. Just send me a message through the board and I'll send you address and contact info.

Regards

 

[Dave8338]

Please forgive me if I missed something, but have you gone through the carbs and cleaned them yet? I only ask, as this is a MUST, prior to getting the "old girl" feeling frisky, gain.

 

[Rudi]

Fair enough...the fella who sold me the bike said he cleaned the carbs thoroughly this Spring. He had street bike and had bought the GS for his wife who simply didn't like her. He was quite honest with me in his dealings and I believed him regarding the carbs. I drained the tank and put in fresh gas with fuel stabilizer/carb cleaner.

 

[mike_of_bbg]

Ah. So by "intake boot" in your earlier post you probably actually meant your airbox vent hose? Airbox as in that wondrously odd black plastic box between your metal air filter box and the carbs?

Did you have fuel dripping down from any of your carb bowls?

Is your oil overfull? Does it smell like gasoline?

Might want to give the float bowls a rap with a block of wood. Sounds like you might just have a stuck float needle. That might explain the gas, if not the high idle...

A "thorough" carb cleaning to the folks on this board has little relation to what most would consider a thorough carb cleaning. As in, complete disassembly and 24 hours min per carb soak in your choice of carb cleaner (usually Berryman's or Gunk). No rebuild kits, but fresh o-rings from Robert Barr (www.cycleorings.com).

Ah, Harrisonburg - or as my wife knows it, home of the closest Kohl's