Idle issues

[haggis905]

First off, happy holidays to all!

I recently purchased a 1982 GS550L that had been sitting in someone's garage for 15 years. Before I started any repairs, I found this site and have to say thank you to everyone that contributed information. I researched all the things that I might need to do to get the bike running again, and here is where I am at now:

tore down the carbs (BS32SS) to seperate components and cleaned them thoroughly (following the instructions on the Carb Cleanup Series). When I thought that everything was 100%, I recleaned them again, just to make sure all the nooks and crannies were clear, since it sat for so long. Once finished, I used the rebuild kit for o'rings that I purchased from Robert Barr, put everything back together, checked all float levels, then did my bench sync, and put the carbs back on the bike.

The bike will immediately start, but then idles up to 3500 rpms, with no choke. When I hit the throttle, the engine nearly quits. When I roll off, it goes back up to 3500 rpms. The airbox is stock, with a new K & L filter that has been oiled as per instructions, with the cover on. There are no leaks around the intake boots, everything is set properly; floats, pilot screw, etc. from information I found here and in the manual. If I drop a rag over the air intake (one of those red ones you buy 30 for $5 at your local autoparts store) the idle immediately drops down to 1100 rpms and throttle responds perfect. All 4 pipes are hot, no misfires, etc.

I know I am missing something simple, but for the life of me I can't figure it out.

TIA

Jay

1982 GS550L
float height 22.4.+/-1.0
pilot jet 1/2 turn out
pilot screw 3.5 turns back

 

[duaneage]

Could be a problem with the slides. Hard to tell assuming you did everything else right.
Are you sure the choke is adjusted properly?

 

[haggis905]

The slides move smoothly after the cleanings, and as far as I know the choke is adjusted properly. I checked online to see if maybe there was something missing from the airbox cover, but it is complete. Is there a specific way that I can make sure that I have the choke adjusted properly? I could'nt find anything in the manual.

 

[DimitriT]

Check the plugs for fouling. Are you sure there are no intake leaks?

Pilot jet (did you mean idle mixture screw?) at 1/2 a turn seems too lean. Back them out another 1/2 to 1 turns. The idle should increase. Use the idle throttle knob to adjust it back down to about 1500 RPM. Repeat for all carbs.

Maybe you can get a good enough idle to sync the carbs. Everything seems to work better once you do that.

Also check your petcock by sucking on the tubes. Make sure there are no leaks.

The choke doesn't have an adjustment but it is obvious when it is pushed all the way in at the rail doesn't go any further.

BTW, welcome to the forum. Nice to see another 550LZ come to life. I had mine out today in 35 degree cold doing 75 on the interstate. Took her "above the speedometer" a few times just for yucks. I love the sounds it makes when you open up above 70.

 

[haggis905]

DimitriT,

I checked the plugs for fouling and 1 2 and 4 are definitely showing signs of carbon fouling. 3 is showing normal conditions, and I did the wd40 test around the intake boots but did not get any surges.

The idle mixture screws are at 3.5 turns out, but even if I set them 1 turn out I get the same results. The pilot jet was set to 1/2 turn out after reading another posting that had similar issues (I was ready to try anything at that point). I noticed tonight that one of the boots from the airbox to the carb has several small cracks under the clamp, but the rest of the boot seemed ok. I didnt get a chance to look at the others since it got dark, but I can do that in the morning and get back to you.

The petccock is brand new and the choke rails are all the way in. There is a solid draw of air from the top of the airbox, so am I correct in thinking that this is a fuel issue of some sort, maybe a plugged passageways?

FYI, I cant even imagine riding in 35 degree weather! (but then again, i'm in California!!) You are one brave man!

 

[DimitriT]

I'm still not sure what you mean about the pilot jet being 1/2 turn out. All jets should be all the way in as far as I know.

Clogged fuel channel would give you lean conditions. Rich conditions (as indicated by the fouled plugs) are due to things like leaky needle valves, bad float settings or poorly adjusted idle mixture screws.

I don't know if leaky diaphrams would cause rich or lean but thats something else to check. You said they the sliders are moving smoothly. I had a problem with a slider where it would hang up due to some dings on the downwarn facing edge.

When I was doing the carbs on my bike I did run into an odd problem on carb #2. The idle mix screw had been torqued down way too much by some goober and the hole was reamed out as a result. No matter what I did to it, that carb would never idle right and I was lucky to find a replacement.

 

[KEITH KRAUSE]

Because it's easy and probably needs doing anyway, I suggest a good bench re-synch. Be sure the throttle valves are set per the manual and the bike idles at 1,000/1,100 rpm's. If they're set correctly and operating smoothly, you have an intake leak. Your problem is most commonly an intake leak but I'd still check the synch anyway.
Also, if the bike's rpm's rise even more as the bike warms up, this indicates an intake leak, not a poor synch. Intake leaks can cause hard starting and higher rpm's while the motor's cold, but once it warms up, the rpm's rise much more.
Intake leaks are not always exposed by testing with water mist (my choice) or WD40 or whatever. A bad manifold o-ring or manifold leak can be hard to reach. Takes just one cylinder to cause your problem.

 

[duaneage]

Check the screws in the manifold that plug the holes ued for syncing the carbs, sometimes they leak air.

 

[damnitall]

I want to echo the recommendation by Mr Krause. Check for air leaks, it sounds like a lean run. My '81 showed no outward signs of air leaks but idle rpm rose with engine temperature. Idle speed was 2200 - 2500 at normal temp. So when I last pulled the carbs I found the boots were cracked along their ends. Numerous cracks extended inward from the lip. They were covered by the clamps while installed and only obvious on removal. Cracking was worst on the engine end of the boots.

Since I wanted to reassemble and not try to find replacements (always in a hurry) I got some silicone gasket sealant and gooped them. Made sure to minimize interior goop to prevent entering cylinders. Idle behavior has been perfect since then.

 

[kahuna]

intake leaks

intake leaks

wouldn't a spray like carb cleaner or starter fluid lightly shot expose an intake leak by increased rpm's immeadiately after sprayed ?

 

[KEITH KRAUSE]

Re: intake leaks

Re: intake leaks

wouldn't a spray like carb cleaner or starter fluid lightly shot expose an intake leak by increased rpm's immeadiately after sprayed ?

Supposed to, if you hit the leak which can be hard to reach.
I always use a fine water mist. The rpm's will drop with water. Much safer and cleaner than flammables and won't dry/harden rubber parts.

 

[toymechanic.]

Re: Idle issues

Jay

1982 GS550L
float height 22.4.+/-1.0
pilot jet 1/2 turn out
pilot screw 3.5 turns back[/quote]

Jay,

I not sure about your carbs but mean only have adjusting(fuel/air mixture) on the top just in front of the diaphram plates, on the intake throats. Your pilot jets should be seated and torqued down(not necessarily with a torque wrench). If you have your pilot jets back off of seated then that is a rich result, because fuel not only is going thru it but around it too. Take the bowls off and tighten the pilot jets and see if that fixes your problem.

Gary

 

[haggis905]

Re: Idle Issues

Re: Idle Issues

Gary,

Thanks for the information. Sorry for the long delay/follow-up, have been spending all my time helping my soon to be 1yr old walk. I have some updated information on the bike.

I picked up a used set of carbs since I broke one of the float towers off of #1 (arrgh!!) shortly after my last post and lucky me, they were off of a 1982 GS550 and in good condition. Took them through the carb cleaning process leaving each one in the cleaner overnight. Cleaned them up with carb cleaner, including the wire brush tip through the pilot jet hole, etc. and verified everything was clear with carb spray before using the compressed air. I benched synced the carbs as per instructions found on the site, and felt that I had done a pretty good job of it. Oh, and I installed new o-rings. Checked for fuel in the carbs and everything looked good.
I then removed the intake boots and checked them for any cracks, etc. but could find none (they are not hard but soft and in good condition). I installed the new o-rings for the intakes that I ordered and made sure that I cleaned where the intakes met metal, since it looked like someone put some sort of sealant on them.
I then rechecked the new plugs for spark, and they all fired fine. Installed the rebuilt carbs, connected them to the airbox (with the lid on and the new K and N filter with Duaneage's recommendation of 1oz. oil from a previous thread), plugged the vacuum on #2 (I am using an external fuel tank) and verified that the battery was showing a full charge before attempting anything.
Lastly, I seated the pilot screws gently, then backed them all out 2 1/2 turns. As soon as I pressed the starter (with the choke on) it instantly caught and shot right up to 6K rpm. Closing the choke brought it down to about 4K. I tried adjusting the idle with the adjuster under carb #3, but it had no effect. Hit the throttle no more than 1/4 turn and it bogs down immediately. So I sprayed water around the intakes and the airbox, but no change.
I also tried something that I hadn't done before, which may give someone an idea as to whats happening. I removed the lid to the airbox, with no change, including the 1/4 throttle. Same thing with removing the air filter.

So, at this point, I am at a total loss as to what is happening. I purchased new clamps for sealing the carbs to the intakes and airbox, which I will install over the weekend. I talked to the service tech at the local dealership, and even he was at a loss after I explained everything to him, including bringing him the pilot jet, needle jet, main jet and diaphram for his inspection.

I want to bring her back to life, but need a small miracle at this point. Oh, one more thing I forgot. I bought a manometer to sync the carbs, so I can get a reading this weekend if that will help at all.

Help!!!!!!

 

[tconroy]

i would use wd 40! it is not as flammable and will let you know after a couple of seconds of spraying. My idle also jumps after being warmed up and i no Its my boots. i will try the silicone and see what happens

 

[jimg]

Did you bench sync the carbs before installing them. If the main idle knob doesn't affect it, maybe you have one carb (or more) out of sync.

 

[haggis905]

I did do a bench sync before the install, Jimg. That's what I was thinking also, that somehow I was off, but I followed the instructions for doing a bench sync from the Suzuki Service manual I have for my GS750 (came with the bike), and from the information that I have read in the GS forums. I could take them in and have them synced at the Suzuki dealer, but what would I learn then?

This weekend I am hoping to be able to check the timing and get a compression read and use the vacuum sync tool to see how far off they are.

 

[jimg]

I did do a bench sync before the install, Jimg. That's what I was thinking also, that somehow I was off, but I followed the instructions for doing a bench sync from the Suzuki Service manual I have for my GS750 (came with the bike), and from the information that I have read in the GS forums. I could take them in and have them synced at the Suzuki dealer, but what would I learn then?

This weekend I am hoping to be able to check the timing and get a compression read and use the vacuum sync tool to see how far off they are.

If the problem is in the carbs, the only other thing I can think of is the choke setup. Part of the choke valve's purpose is to open a bleed hole underneath the slide diaphram so the slide can't raise, at least on my 1980 carbs.

You might check and make sure the cable is allowing the choke valves to return all the way in. You might also check the choke rail to make sure everything is set correctly, i.e. the set screws are in the depressions that make sure they are aligned.

The choke setup could explain the high idle and bogging.

 

[haggis905]

I checked the choke valves and they move in and out perfectly, same as the old carbs. I didn't remember this until reading your post, but I was having the same exact issue with the original carbs that I rebuilt. Except those were really gummed up from gas being in the bowls, etc. for many years (the gas that came out of one bowl was green, and another was deep orange in color). The replacement carbs are in good condition, but I still cleaned them thoroughly.
The choke moves smoothly and if applied when the engine is running will increase the rpm's dramatically.

 

[jimg]

I checked the choke valves and they move in and out perfectly, same as the old carbs. I didn't remember this until reading your post, but I was having the same exact issue with the original carbs that I rebuilt. Except those were really gummed up from gas being in the bowls, etc. for many years (the gas that came out of one bowl was green, and another was deep orange in color). The replacement carbs are in good condition, but I still cleaned them thoroughly.
The choke moves smoothly and if applied when the engine is running will increase the rpm's dramatically.

I'll be honest, other than motor issues the only thing I can think of is that the slides are not raising when you open the throttle.

This sounds funny and complicated but its really pretty easy, except for removing the carbs again.

There is a wide and narrow opening in the carb throat on the airbox side. It is at the top of the throat on my carbs. Air moving into this opening is what causes the slides to move. If you blow into this the slide will move upwards. It doesn't take as much wind as starting to blow up a balloon. Give a real good puff and you'll hear the slide hit the top.

Then, on the butterfly side, you'll find a small hole in the carb throat between the butterfly and manifold. If you open the choke, air will flow throw the slide diaphram and out this hole. With the choke open and you blowing into the air opening, put your hand over the throat on the butterfly side and you should feel the air come out. With the choke open it takes a lot more air to get the slide to raise! Close the choke and the air should cease flowing out this opening.

If this works ok, then something else is wrong!

 

[haggis905]

Thanks, I will try that tonite when I get home and post the updated information. I have blown gently into that opening before and all diaphrams rose quickly, but I have not checked with the choke open.

Thanks