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'81 GS550 Carb Settings Confirmation

  • Thread starter Thread starter vegas
  • Start date Start date
V

vegas

Guest
Hi guys,
I have poured over these forums looking for settings and tips and I have learned so much already. However, I am trying to find settings for my carbs I have reworked. I've sort of pieced together the settings through many post. So I'm looking for confirmation on various turn settings for the following:

Air Screw(air box side) - 2 turns out?
Pilot Screw(in fuel bowl) - 1 turn out?
Main Jet screw (in fuel bowl next to pilot screw) - #?? turns out?
Idle Mixture Screw(engine side before the intakes) - 2.5 to 3.5 turns out?

All my carb parts are stock and rebuilt with K&L kits. I've dipped and stripped them so hopefully we'll be good to go. I found this nice list of information on the specifications thread, but as I am not a mechanic some of this just doesn't make sense to me (please forgive my ignorance).

Thanks in advance for the help.



GS550 (80-82) the specs are for the CV's

idle r/min 1100-+/-100r/min
carb mik bs32ss (4 seprate 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 adjusable 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)

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.
 
Any chance you still have the stock jets? :-k

You will probably be better off putting them back in instead of that K&L stuff.

Now, to the settings:
Air Screw(air box side) - 2 turns out?
That is not an "air screw", it's a "pilot air JET" and gets screwed in snuggly.
Pilot Screw(in fuel bowl) - 1 turn out?
That is not a "pilot screw", it's a "pilot fuel JET" and gets screwed in snuggly.
Main Jet screw (in fuel bowl next to pilot screw) - #?? turns out?
That is not a "main jet screw", it's a "main JET", and gets screwed in snuggly. (are you seeing a pattern here?)
Idle Mixture Screw(engine side before the intakes) - 2.5 to 3.5 turns
out?
NOW we're talking 'adjustable'. :clap:
If you have the stock airbox and exhaust on the bike, start with about 2.5 turns out from lightly seated.
When the bike is warm, slowly turn each one, listening for highest RPM.

.
 
Steve said:
Any chance you still have the stock jets? :-k

You will probably be better off putting them back in instead of that K&L stuff.

Now, to the settings:
Air Screw(air box side) - 2 turns out?
That is not an "air screw", it's a "pilot air JET" and gets screwed in snuggly.
Pilot Screw(in fuel bowl) - 1 turn out?
That is not a "pilot screw", it's a "pilot fuel JET" and gets screwed in snuggly.
Main Jet screw (in fuel bowl next to pilot screw) - #?? turns out?
That is not a "main jet screw", it's a "main JET", and gets screwed in snuggly. (are you seeing a pattern here?)
Idle Mixture Screw(engine side before the intakes) - 2.5 to 3.5 turns
out?
NOW we're talking 'adjustable'. :clap:
If you have the stock airbox and exhaust on the bike, start with about 2.5 turns out from lightly seated.
When the bike is warm, slowly turn each one, listening for highest RPM.

.
Click to expand...

done and done......:clap:
 
Ok but...

Ok but...

Thanks for replying guys, but honestly, "snuggly" seems contradictory to everything I have seen so far. So from snuggly I take it to mean turned all the way in and the only thing I should be adjusting is the idle mixture screw?

And yes, i am using the stock jets.
 
vegas said:
Thanks for replying guys, but honestly, "snuggly" seems contradictory to everything I have seen so far. So from snuggly I take it to mean turned all the way in and the only thing I should be adjusting is the idle mixture screw?

And yes, i am using the stock jets.
Click to expand...

This is correct. The early 550 model has VM style carbs and on those there is an adjustable pilot fuel screw and pilot air screw. Maybe you are getting confused between the two. The BS/CV carbs only have one adjust - the pilot (or air) screw (my 550 ran best at 3.5 turns but you can start at 2.5). And make sure you replace the intake boot O-rings while the carbs are off if you haven't already done so (they are sure to leak if they are the originals).
 
Last edited:
I see now...

I see now...

Yeah, I have the CV carbs(thanks for the clarification). So when I get home, I'm screwing in all the jets snuggly and turning out idle mixture to 3.5. I also read a post on a hard starting 750 and to make sure the fuel bowl gasket isn't covering some holes for the choke to work. Good info there too.

And yes, I've got new intakes and o-rings on. That seemed like such an easy thing to do I figured I might as well do it.

Thanks!!
 
Last edited:
Almost but not quite

Almost but not quite

So I got everything in order, went with 3.5 turns and didn't start well. Went up to 4 turns and then she started with the choke. Got her running and went for a spin, a little idle, not too great though. While driving there is no power and she just bogs down when I pull the throttle. I thought maybe the mixture was still too lean, so I went to 4.5. Then it was back firing and dying, could get it to idle at all. It did have a little more power.

I do have new O rings on the intakes, all the seals around everything seem to be tight so I'm not sure what I'm missing.
 
Do you have the airbox installed? Any mods?
 
No mods. The bike is stock as far as I can tell. Airbox is installed.
 
Not sure what to suggest... Can say that it's normal for your GS to require choke when first started. Typically, GS bikes requre choke for a short period of time until the engine gets a little warm before it will run properly without the choke.
 
Reocurring pattern.

Reocurring pattern.

I see a re-occuring pattern:

Ok, I did get it running again this afternoon, but here is a consistent trend. No matter what setting I put the mixture screw at 4-5 the bike starts, runs really well for about 2-5 minutes. On the center stand I cycle through all the gears, it appears to have good power, but then after about 5 minutes, it loses power and I can't get it to go above 3k RPM's, it just bogs down and chokes. It keeps doing this for about another minute or so, then dies and won't start again.

It seems like it isn't getting fuel after a few minutes, but why? If it starts, runs well, why does it bog down after a bit. I think if I fill the fuel bowls again and wait for awhile it'll start. This has happened about three times now.

Also, after the bike dies, choke doesn't seem to help it either. Do I have it the other way around? Am I flooding the bike?

Any help you guys can give would be great! Thanks!
 
Pull a plug after it dies and see if it's wet or dry. If the plugs are dry you might want to remove the float bowl drain screws to see if there is gas inside. Could be your petcock is not letting enough fuel through. Setting the petcock to prime might help as well, as well as making sure the gas cap is properly venting.

Good luck and don't give up...
 
Thanks Nessism, I was getting close to giving up. Petcock was just replaced with a new one cuz the old one leaked. So hopefully that isn't the problem. How do I check the gas cap venting? I'll check the plugs.
 
You can see if the gas cap is the problem by simply lifting the cap next time it bogs out.
If you hear a "whoosh" when you open the cap, it's not venting properly.

.
 
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