3.5 turns back? (air screw)

[Clumzi]

So I'm looking at my carb specs that I got from this page and I just want to make sure I understand. 3.5 turns back on the air screw (mixture screw, what have you) is the general starting point for air screw adjustment. Does that mean 3.5 turns back from reasonably snug to the bottom? -nick

[Steve]

NOT "reasonably snug".

Just "lightly seated".

Opinions vary between two and three turns, 3.5 seems a bit much. Of course, this is just a starting point. After the bike is warmed up, you will tweak them to perfection.

.

[Clumzi]

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.

That is where I'm getting my info from. I just finished my first carb (after practicing on the 650 carbs), "snugged" the mixture screw (not tight or anything, just to where it seemed to want to stop) and backed it up 3.5 turns per the instructions there.

But that's the idea, right? And then get the bike warmed up and tweak it once its warm... does it matter which carb I begin with? -nick

[Nessism]

My old '81 550T ran best with the screws at 3.5 turns. That said, they should be tweaked for best running as a matter of course.

[Steve]

... does it matter which carb I begin with? -nick

For mixture tweaking, order is not important.

For synchronizing the carbs, the suggested order is to match #2 to #3 (the 'master' carb), then #1 about 0.5cm above 2&3, then #4 to match #1.

.

[boba]

idle screws

hmmm looks like this is where im going to be in a day or so. i dont know even if my 550 is going to run or not, i would be happy if it just fired.

but how ever i have a new head gasket for it and i bought the little washers seals that go in each corner because they came off my old gasket. the new one has what looks like the seals made into it already attached. so do i need to put in the 4 single ones that were seperate from my old gasket??

[Zooks]

Tighten 'em down 'til they snap and then back them off half a turn.


This was my dad's favourite joke when I was kid (if I asked him any technical question).

[waterman]

Give it a go at 3.5 turns, but remember the idea of fine tuning is to get a smooth even idle. Search the forum for highest idle method. Basically adjust the mixture screw for each cylinder until the highest idle speed is observed. At this point, turn the idle speed screw back to normal idle speed (1100 rpms or so) and adjust next carb again to highest speed.

I have a hard time either hearing the rpm change or seeing the tach movement. If this is the case, you may just set the mixture screws at a certain level and leave them alone. I have used colortune spark plugs with some success but don't believe it is truly necessary. You can usually get them close enough by observing how smooth engine idles and sounds. Hope this makes some sense, once you have done it a few times, it get easier to tell.