Suddenly stopped idling mid-ride

[Guest]

Hello all,

So this is a seemingly weird issue, but my 1980 GS550e suddenly stopped idling mid-way through my ride. I was stopped at a light and was idling fine. I accelerated somewhat quickly (up to maybe 7k RPMs). Then when I went to the next light 3 minutes later, my bike instantly stalled upon pulling in the clutch. The RPMs went all the way down to zero, not even pausing a little at the usual 1100 RPMs. Then I pulled off and began messing with the bike. It will still idle when chocked, but dies as soon as the choke is turned off. I got home by giving it some gas and keeping the RPMs around 1500 when the clutch was pulled.

Usually I would chalk this up to the fuel adjustment, but I the fact that it stopped idling mid trip makes me think that there is a bigger issue, like maybe a cylinder stopped firing. I have been riding this bike regularly and have been surprised by how well it idles previously.

background on the bike: all drivetrain is factory. 8,000 miles on it. Oil and air filter recently changed a few weeks ago. Carbs cleaned and spark plugs changed 150 miles or so ago.

anway, any information on where to begin would be a great help. I am new to bikes so I'm not that mechanically inclined, and trying to minimize my cost to get this thing back on the rode for the summer.

[tom203]

Start with simple test of petcock to make sure it isn't dribbling fuel down vacuum line to #2 carb and fouling it out. Do you still here the infamous leverless 1980 petcock? So spark plugs are new, how about those plug caps?
How thorough was your carb clean? It's possible that one carb has gummed up its idle circuit after some running.

[Steve]

Has the idle returned to 'normal'?

It's also possible that the idle speed control knob has vibrated loose and backed off a bit, just lowering the speed.

.

[Tenshots1]

Hmm I'm not sure what a "leverless peacock" is, but I do have a little lever on my peacock moving from reserve to on etc and it seems to be functioning fine. Regardless, I will pull the vacuum line and look for fuel.

Steve, I can get the bike to idle somewhat normal with the choke engaged, but obviously it takes some messing with. It did seem to initially start somewhat fine after the incident with the choke engaged. Then I rode for a few hundred feet and it was dying again. The previous owner cleaned the carb, so I'm not sure if he paid to do so or did it himself etc. plug caps appear to be stock, but I'm not sure. I would understand these becoming issues if I went out to ride after it sitting for awhile. I'm just surprised that I've been riding it frequently the past couple weeks with no idle issues and suddenly it happened to be mid-ride. Where is this "speed control knob" that you are referring to? I thought idle was just adjusted by the fuel adjustments on the carb?

[Steve]

The idle speed control will be found at the bottom of the carbs, between the float bowls of #2 and #3. It is usually easiest to reach if you are sitting on the bike and reach down with your left hand. You will only be able to push the edges of the knob with your fingers, not grab it and turn it. Yes, the fuel adjustments will affect the idle speed a bit, but that is not how you adjust the overall idle speed. You get the mixtures set properly, then set the speed. Your bike should be about 1100 RPM.

The "choke" control merely opens up another circuit in the carbs that provides its own fuel and air supply. Once the engine has been warmed up enough to run without "choke", you should not need it until the engine cools off sufficiently again (several hours).

ANYTHING the previous owner told you is likely something that was made up to sell the bike, so assume that it hasn't been done until you do it yourself or are physically there to watch it being done.

.

[Tenshots1]

Thanks Steve. I totally agree about POs not being trust worthy. But currently I live in the city and don't have a real place to do extensive work on the bike and can't really pay to take it into a mechanic since the wife is already grilling me about it. I'm hoping to keep it operational for the summer and dig into it during winter. Anyway, I will check out that knob you're referring to. I have chubby hands so hopefully I can get in there. Is this knob something that usually comes loose? I'm just worried maybe this is a big issue. Is there an easy way to check if all 4 cylinders are working correctly? Or is there a write up of things to check around your bike. I would hate to simply increase the idle and risk making a problem worse.

[tom203]

Watch out for your chubby hands, these things get hot! Pic from Basscliff

http://i156.photobucket.com/albums/t40/basscliff/maintenance/carbs-fuel/intake_repair36-1.jpg

[Tenshots1]

Thanks for the pic! This entire photobucket account is full of Gems.

[tom203]

Not me, Basscliff's info warehouse! Surely you've seen it......

http://members.dslextreme.com/users/bikecliff/

[Tenshots1]

Yup, i have seen it. I must admit its overwhelming though! My last project was a jeep wrangler that I did a lot of work on, and I swear it was somehow much simpler.

[Tenshots1]

Hey guys,

just wanted to to post the solution to the problem I was having incase anyone was curious or had the issue themselves: it looks like the PO had screwed the idle screw all the way in so that it wouldn't idle at all. Then, to compensate for this, he adjusted the throttle cable nut above the carb so that the throttle was always slightly applied. The nuts holding the throttle adjust the came loose and rid itself of this tension, stopping the idle.

So, I went and tightened the throttle adjustment how it was so that there was no tension at zero throttle. Then, I adjusted the idle screw correctly. I am now back on the road and the bike seems to be operating better than before.