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1978 GS550E running too rich - where's the mixture screws?

  • Thread starter Thread starter adamb
  • Start date Start date
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adamb

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Hey guys, I just joined up on these forums. A few weeks ago I got a '78 GS550E. The previous owner said it sat unused outside for quite some time before I got it. He said he cleaned out the carbs because the floats were stuck, or something.

I put a few parts on it (Clutch cable, rear tire, new plugs, air filter, fuel filter) and I have a few plans for the long winter (rear master and slave cylinder, valve adjustment) but right now, I'd like to try to get my bike running leaner because I think it's running too richly.

Even when it's running warm, the exhaust smells like unburnt fuel, and all four plugs are uniformly blackened (the old plugs were the same way). I've put a couple hundred miles on the bike, and it runs fine more or less fine, although I think it's running rich - but I don't know how to adjust the mixture on the bike. Is there a screw or anything I can turn on the carburators to make the bike run leaner?

And with that: How lean is too lean? How do I know when it's running right? My summer riding length is two months long, so I don't want to get into any huge projects while I still have heat and daylight. Ideally I'd be able to tinker with screws, get it running a bit better, and then be "done" with it until winter starts and it's too cold to ride (Roughly middle to late august). My bike gets ~43 MPG at the moment, which is good, but I imagine it would do better if it wasn't running so rich.

Thanks,

Adam

(http://www.mtaonline.net/~adambultman/1978suzukigs550.jpg)
 
First of all,
welcome1.gif


How long was the bike sitting before you got it? Chances are that it needs a good carb cleaning rather than some screw-tweaking. There is a good chance that some of the air passages inside the carbs are plugged, and no amount of screw tweaking will make any improvement.

Sorry about your limited riding season, but doing a good cleaning will minimize your frustration and downtime.

BassCliff will be along with his little 'welcome' shortly

.
 
I doubt it would run that rich unless the float level has been changed or different main jets were installed.
A dirty air filter can make it run rich, did you check it?
Also check the spark and the gap on the plugs and make sure they are gapped right.
 
Pssst...valves....have you checked them for propper clearance? It may not have anything to do with your current rich condition, but its silly to mess with carbs unless you're certain you're in spec on the clearances. Its quite possible the PO never did, and as they got worse, the bike started running leaner and leaner, therefore his fix was to fatten up the fuel delivery. Could be completely wrong too, but as i said, if you get it all dialed in now, you'll likely have to redo it when you adjust the valves (and you WILL have to at some point)
 
Steve
I did a complete carb strip before running the bike took every thing dow except for the diaprams used cleaner and blew out all the air passage ways but to be honest
the carbs look in mint condition internally
oh yeah WOW! thanks for your quick reply and input
cheers Roy
 
Last edited:
Gear Head
If you read the thread right thru you will see I fitted a new air filter and the bike ran
even worse than before much richer, plugs are gapped correctly and are new out the box,I did say the carb air box has holes driled in the top and the filter was missing when I got the bike so this may indicate someone rejetted for k&ns or such like?
cheers Roy
 
Cafe Kid
Will do those have to be right can you give me the clearances please?
Thanks Roy
 
Don
Coil Relay mod? please enlighten me mate? my bike runs points/ condenser not electronic module cdi
best regards Roy
 
Just uses a relay to power the coils directly, instead of running it through a bunch of switches, connectors and wires. Provides a higher voltage to operate the coils, and a more reliable spark. Works equally well with points or electronic ignition.

Lots of info on how to do it, search relay mod.
 
Steve
I think you may have pointed me in the right direction here,reading that carb rebuild
article tells you on page 10 how important pilot idle screw ajustment is and to play with the mixture till the bike "leans out" this may well be where the problem lies
Also upon removing my pilot air screws I found no O rings on the screws at all on any of them!, even though my carbs are the CV Minkuni type and not the same as the CN type in the article they look almost the same my idle screws have a very fine point at the end which is diierent than the second set in the carb article does any one have a picture of the CV type air screws with the O rinhgs fitted so I know where to fit new ones?
many thanks group were getting there Roy
 
Adam
OOPS! THINK I BUTTED IN ON YOUR THREAD PAL!
Sorry but I posted a similar type message to yours and assumed it was my thread but hey we both maybe looking at the same problem here
once again my sincere apologies
Roy
 
Guys
Just pulled all the air ajustment screws out and checked the O rings they are perfect
turned em down to half a turn still have the same problem
seems like this guy changed the jets so I will pull the carbs and change them back to standard
cheers Roy
 
I don't know exactly how long it had been sitting, but the guy who owned it bought it when it had sat for a while, and then he didn't do much with it. I think he took it out every now and then, but I believe it spent most of it's time sitting perfectly still. The guy had another bike (A triumph) that he rode - and he was only selling this one to make room for a new bike (Also a triumph). He never rode this bike regularly. So the bike has been sitting probably for the better part of 5 years, with on-and-off taking-for-spins.

I replaced the air filter, and I soaked it in oil (as I was instructed by something). It's not dripping oil, but air should be passing through it just fine.

I know that I'll need to be doing a carb rebuild. I knew that coming in. But, I'd like to at least get the rest of the month in before tearing it down and having parts strewn about my garage - seriously - I have probably a month's left of riding before it gets too cold - and there's about 1 good day of riding out of 5 up here this summer.

I also know I need to get the valves adjusted (that'll be quite the task - I've never done that before - OR a carb rebuild, for that matter) but for now, they stay where they are at, for reasons I've already cited.

SO! On to my tweaking. Chime in if you wish.

All four plugs were uniformly black on the ends, with carbon buildup. Using the previously mentioned carb rebuild PDF, I have been messing a bit with my mixture. I just got back from a quick ride after having adjusted the screws 1/8 to the *left* (Which should mean leaner) and listening for popping while engine braking, or bogging out while accelerating. When I got back (making sure not to idle the bike up the driveway, and maintain ~3500 RPMs up my street) I pulled the two outermost plugs; plug 4 (far right, as I'm sitting on it) is still black and has carbon buildup, plug one (leftmost, as I'm sitting on it) is "cleaning up", and electrode and other side of plug where the spark arcs to is "clean" - it's not carbony anymore. I left the mixture on carb 1 the same, on carb 2 I turned the screw out another 1/8 turn. I did notice a bit less power on the low end during this ride.

I don't know what my plugs are supposed to be gapped at - I have *a* GS550 owner's manual, but it's for an '82 GS550L, which isnt' the same. If you wanna tell me what my gaps should be at, I'd change 'em right now.

Again, I know I need a carb rebuild - and I also probably should drop in a new clutch, since I evidently have enough power in the high end to slip it (and the clutch cable is brand new) - but I want to wait on that. If that means I have to completely re-tune the mixtures - that's fine - I image after a complete carb cleaning/rebuild I'd need to do that, anyway.

Any assistance is appreciated. This winter I'll be picking up a clymer for this bike so I can do everything in my garage - except carb syncing - that appears to require special hardware I may not be able to rent here in Alaska.
 
B8ES plugs? If so i think even for your 550 its in the .26-.30 gap range? SHoot for .28 and call it good :)
 
CafeKid: Yes, B8ES. They were not gapped at ~.028, so I gapped them at that. They were probably closer to .024 or .025, if even that. It's hard to tell with my crappy little 50 cent gapper.

As for the other plugs: The other two plugs (in cylinders two and three) are also "cleaning up", although not as ... quickly as the other. Perhaps cylinder 1 is running too lean.

At any rate, if it's not raining, and it's warm enough, I'll ride the bike to work tomorrow (~20 miles). I hope that's not far enough to cause any damage if I'm running too lean.
 
adamb said:
CafeKid: Yes, B8ES. They were not gapped at ~.028, so I gapped them at that. They were probably closer to .024 or .025, if even that. It's hard to tell with my crappy little 50 cent gapper.

As for the other plugs: The other two plugs (in cylinders two and three) are also "cleaning up", although not as ... quickly as the other. Perhaps cylinder 1 is running too lean.

At any rate, if it's not raining, and it's warm enough, I'll ride the bike to work tomorrow (~20 miles). I hope that's not far enough to cause any damage if I'm running too lean.
Click to expand...

You'll know if you're TOO lean (well, any lean is TOO lean IMO, but damage is less likely if SLIGHTLY so) If your pipes are blueing, the bike temp gets unusually hot, popping thu the pipe, hanging idle. All symptoms of leaness. keep an eye on things. You, idealy, want your plugs clean with a slight brown colour going down the electrode ceramic in the center. Ashy white plugs, super white centers, or speckled centers are lean/detonation signs. Buy a new set and do some plug chops. Thats the best way to tell where you're at.
 
Cool, thanks CafeKid. I don't know if what I have on my plugs (and they are new plugs, less than a week old) is signs of leanness or detonation, or what - I'm not ver knowledgeable about it.

At any rate - I'll keep an eye on it. I'll look for bluing or any other signs (or sounds) of too lean a mixture, detonation, etc. I certainly don't want to blow up my bike. Maybe i'll just turn my carbs' mixtures 1/8 to the right... :)
 
Tis better to be a bit rich than a bit lean. Too rich can also be bad, but generally you'll know that cos the bike will run like a slug. Lean, for me anyway, is harder to detect, cos just slightly lean, and the bike will run like a bat out of hell, for a little while.
 
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