This Beats All

[REDDY]

As a few of you remember I have been having trouble getting my 80' GS 550 L to run right. I have cleaned and adjusted carbs till I'm blue in the face. I installed new o-rings and made sure every part is per manual. I have new plugs, hoses and carb-to-engine boots. The petcock works perfectly. Plenty of fuel flow. Sealed carb-to-airbox with silicone.

Before it would run up to 5K and fall on its face. The pipes started to turn dark.(not blue yet) A plug chop showed slightly rich on 3 and 4. I don't have my sync tool yet (ordered) but I bench synced as well as i could.

I fianally decided the air flow wasn't there so I removed the air-box lid. It ran better. I removed the foam filter, It ran better still. I then removed the screen. It runs even better.

WHAT IN THE PLUPERFECT HELL IS GOING ON? I was under the impression that opening the air-box would result in a very lean condition. It does look like it is lean but not excessively. WHAT AM I MISSING?


I have been a mechanic for fourty years. I currently run a 2007cc VW that I built. ( high 14's) This has me talking to myself. HELP !!!

[Highcountry2000]

Just rambling...

I don't have a clue either! Are you sure your exhaust is not blocked by some insect nest, it has happened to me!

Also, I just solved my "hair pulling" carburetor problem... I installed a new set of ignition coils!

Like you, I have been doing this stuff since the early 70's!

Good luck, Bruce

[Dave8338]

As a few of you remember I have been having trouble getting my 80' GS 550 L to run right. I have cleaned and adjusted carbs till I'm blue in the face. I installed new o-rings and made sure every part is per manual. I have new plugs, hoses and carb-to-engine boots. The petcock works perfectly. Plenty of fuel flow. Sealed carb-to-airbox with silicone.

Before it would run up to 5K and fall on its face. The pipes started to turn dark.(not blue yet) A plug chop showed slightly rich on 3 and 4. I don't have my sync tool yet (ordered) but I bench synced as well as i could.

I fianally decided the air flow wasn't there so I removed the air-box lid. It ran better. I removed the foam filter, It ran better still. I then removed the screen. It runs even better.

WHAT IN THE PLUPERFECT HELL IS GOING ON? I was under the impression that opening the air-box would result in a very lean condition. It does look like it is lean but not excessively. WHAT AM I MISSING?


I have been a mechanic for fourty years. I currently run a 2007cc VW that I built. ( high 14's) This has me talking to myself. HELP !!!

Have you adjusted the valves yet? A combo of too little/much valve lash and unsynched carbs will do some very strange things to these bikes. If everything else is set right, removing the aribox cover and filter will cause the issues that you're talking about...my gut feeling is, that if you set the valves and sync the carbs, you'll have it running the way it should. Did you do a bench sync on the carbs yet...this will at least get you close enough to make it run well.

[Nessism]

Maybe someone messed with the jetting/needle setting and set the bike up too rich?? choke stuck?? floats too high causing raw gas to flood into engine?? One way or another what you describe is that the bike is running way too rich and reducing intake restriction, resulting in leaning the mixture, is improving things.

[Planecrazy]

You DID sacrifice a chicken to the voodoo g-ds and dance naked under the stars ... right?:shock:[-o<;-)

Good luck with it!!

[REDDY]

I am considering dancing naked in the light of the moon. I will even make a sacrifice (two pieces of KFC chicken) to the carb fairies. I might even consider offering my left gonad. But since it has functional problems, that might not please them, but I dont seem to have any use for them anymore so why not?

[bwringer]

I am considering dancing naked in the light of the moon. I will even make a sacrifice (two pieces of KFC chicken) to the carb fairies. I might even consider offering my left gonad. But since it has functional problems, that might not please them, but I dont seem to have any use for them anymore so why not?

Too.
Much.
Information. :shock:



As noted above, check the valve clearances. I would also suspect the float heights are set wrong and/or incorrect jets are installed.

With some floats, you're supposed to set the float height at the "step" or "notch" in the float.

Last fall, I corrected a set of carbs on a friend's bike that some past mechanic had set using the top of the float. I have no idea how it ran at all. I also corrected some badly out-of-spec valves, sealed the airbox, set the idle screws correctly, and washed the excess oil out of the over-oiled foam filter. He was quite impressed with the transformation...

These are some ideas to try, anyway.

[bradleymaynar]

I didn't see it in your post, and I'm not sure which GS you're working on, but I was curious as to whether you replaced the air filter. Not that this is going to cure your problems (I believe the other possible cures are better), but it is the easiest thing to replace.

Brad bt

[REDDY]

Thanks for the replies. FYI I set the fuel level with the clear tube method to ~ 2 mm below the mating surface. The valves are in spec with 1 ex and 1 in slightly tight ( .0015 in ) All numbered parts in the carbs are correct per the book. Incidently it is a 1980 GS 550 L.

[Dave8338]

Please...keep your clothes on! :-D Have you checked for exhaust restrictions yet? A baffle(s) that has blockage or rusted out of place will cause the condition that you are explaining. Short of exhaust, or the issues that Brian mentioned, I'm at a loss as to what else would be causing this. One other thought, have you checked voltage output with the bike static and then again when running at 5000 RPM's.

[REDDY]

I haven't checked the exhaust. Ill have to do that tomorrow. Thanks

[first timer]

are you dead sure the carbs are stock set, maybe someone installed jet kit into them, with the 550 cv carb jet kit, you glue little restrictors that come with the kit into the air jets to richen things up.

you verified all this right?

GS 550’s
1980-82

Mikuni BS32SS carbs
idle r/min 1100-+/-100r/min
carb mik bs32ss (4 separate carbs)
id no 47160 (us) 47170 (can)
bore size 32 (1.26)
float height 22.4.+/-1.0 (0.88 +/-0.04)
fuel level 5.0+/-0.5 (0.20 +/-0.04)
main jet #92.5
main air jet 1.6
jet needle (4bel2 us model) (5f42-3rd notch Canadian adjustable needle)
needle jet x-6
pilot jet #40
throttle valve #135
by pass (0.9, 0.7, 0.7 us model) (1.0,0.8,0.8 Canadian)
pilot outlet 0.7
valve seat 2.0
starter jet #35
pilot screw 3.5 turns back (mixture screw)
pilot air jet (us model #150) (#120 Canadian)
throttle cable play …. 0.5-1.0 (0.02-0.04)




these setting apply to all 550 models with the CV style carbs,
Me personaly would try to get the carbs as close to the the canadian specs as possable the US models were lean out so much to meet emissions. the candian specs give the bike a hardier fuel supply.


didn't you go bigger with the mains?

go back to oem mains if so.

-ryan