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GS1000G - BS34SS Carbs - Pilot Screw Setting

  • Thread starter Thread starter DonL
  • Start date Start date
D

DonL

Guest
Hi all,

Been searching for the setting of the Pilot screws on 1980 GS1000G,
BS34SS CV Carbs.

I read the Carb cleaning procedures and performed it on my carbs.
Upon taking out the pilot air screws,
#1 was out 1/4 turn
#2 was out 1-1/2 turns
#3 wa out 3/4 turn
#4 was out 1 turn.

Hmm...doesn't sound right and it ran junky anyways.
So, searching the archives, I came up with:
The 'pilot screw' is 'factory preset' according to the manual, but ours were about 1-5/8 turns out (CCW) from fully seated...fully seated being just gently bottomed out. This is actually a gas/air mix which is controlled
by this screw, affecting the idle/slow system. Experience shows that screwing it in (CW) leans out the mix, and conversely, screwing it out (CCW) richens the mix.
Someone else mentioned that they started with theirs 2 turns out and adjusted from there.
The service manual says to set them at 3.5 turns

My delima is, start at 3.5 turns out, or 2 turns out?
Should they be about 1-5/8 turns out when adjusted properly?

I take it when I'm adjusting them that I'm looking for the best idle speed
without adjusting the throttle plates (eg. base idle with the knob)
 
I start at 1.5. Then do a Keith Krause highest RPM method on each cylinder.
 
Yes, forgot to mention, the bike is bone stock.

I'll try the 1.5 - 2 turns out this evening.

Thanks for assisting. I'll post results.
 
Start at 1.5-2 turns out, but I think you will find that you end up at 2+. Might be 2 1/8 or 2 1/4, but just a bit over 2. 8-[


.
 
chef1366 said:
I start at 1.5. Then do a Keith Krause highest RPM method on each cylinder.
Click to expand...

Can you explain this method a little better chef??
I have an 81 1000G that I rebuilt the carbs on and I'm gonna need to do the carb tuning after I finish other repairs.
 
Tweak one carb till it revs at idle the highest then reset idle stop & attack 2nd carb etc. Repeat till you've done all 4.
 
I dont mean to highjack this thread but does messing with these screws do more to the carbs than adjust for a better idle?
 
tconroy said:
I dont mean to highjack this thread but does messing with these screws do more to the carbs than adjust for a better idle?
Click to expand...

Not really, but...

Adjusting the idle mixture has an effect on the transition from idle to the first hint of throttle. I prefer to adjust for best idle, then bump it a wee bit richer to smooth out this transition (adjust in 1/8 turn increments and road test). This area of the carburetion is important for rapid twisty road travel because it helps you be a bit more smooth when getting back into the throttle to drive out of a corner.

Moving a bit further up the scale to barely-open to maybe 1/8 throttle, you can adjust float height to fine-tune and smooth throttle response in this area. My bike's floats are set a bit richer -- 0.5mm below the range mentioned in the manual. (Less height when upside-down = higher fuel level right side up). If you're really fussy, there's a gadget with clear tubing that attaches in place of the drain screw to show you the actual fuel level in each float bowl.

Adjust float height in 0.5mm increments (yes, you can definitely tell the difference), make SURE they're all set EXACTLY the same, and road test. Don't just poke and bend things until float height is in the ballpark range in the manual. It's well worth the time and trouble set them all exactly the same. You also have to make sure that both sides of each float are set the same. Lots of floats are a bit bent after decades of abuse from neanderthal mechanics.

These tweaks fall under fine-tuning -- the bike should already be running pretty well and must be correctly jetted before you mess with these tweaks.
 
Ok. Maybe I'm a bit slow.
Started with all four carbs and the screw out 2 turns.
See image
I turned them out 1/4 each, no change.
Then turned them in 1/2 turn, no real change.
It was running for about 5 min, and I thought it was getting a bit hot, so I shut it down.
Is this the "idle mixture" screw (annotated on the picture)?

View attachment 2830

(hopefully I did this correctly)

Also, how bad is it when you go to start it up and cyl #4 is full of fuel.
Hmm...can you say "new needle and seat"??
 
Last edited:
tconroy said:
I dont mean to highjack this thread but does messing with these screws do more to the carbs than adjust for a better idle?
Click to expand...
The mixture screws on the CV carbs act as the fine tuning for each cylinder. They basically assist and provide fine tuning for the pilot jet. They are a necessary part of the pilot circuit and have a varied effect on performance from closed throttle to approx' 1/4 throttle position. As the throttle gradually opens more and approaches 1/4, their effect lessens. Their positioning has a much more significant effect on start ups, idling, deceleration, and minimal throttle openings such as steady/lower speeds/cruising around town.
 
Ok...I messed up and started another thread with exactly the same name....
but the info I finally found is:

yippee...finally the pilot screw info was found it in the archives

I'll get the hang of this yet.


Posted 23 Feb 2007 by tfb:

OK, I went through the manual systematically, and here are the settings for the various models it lists:

GS1000SN ('79) --- VM26SS-equipped models --- Air screw 1.0, Pilot 5/8
GS1000SN ('79) --- VM28SS-equipped models --- Air screw 1 1/4, Pilot 3/4

GS1000L ('79) --- VM26SS-equipped models --- Air screw 1.0, Pilot 5/8
GS1000L ('79) --- VM28SS-equipped models --- Air screw 1 1/4, Pilot 3/4

GS1000ET ('80) --- BS34SS (ie. CV carbs) --- Pilot 1 5/8

GS1000ST ('80) --- VM30SS (in Australia) --- Air screw 1 3/4, Pilot 5/8

GS1000GT/GLT ('80) --- BS34SS --- Pilot 1 5/8

GS1000GX/GLX ('81) --- BS34SS --- Pilot "PRESET" Ah yes, there you go, the dreaded "preset" word. But don't worry, in all other respects (jetting, float height, etc.) the carbie data for this model are the same as for the '80 GS1000GT/GLT (above), so setting the pilot at 1 5/8 will be the way to go.

*Naturally* these are just nominal settings, and assume that everything is stock-standard and that your engine is in good condition, clean air filter, etc. So that if you have pods, after-market exhaust system, bored-out engine and so on, you will need to fine-tune things to suit your setup.
__________________
"I see no hope for the future if we are dependent upon the youth of today" -- Hesiod, 1000BC.
Kat1100SZ -- aka 'The Flying Banana'
GS1000S -- aka 'The Magic Carpet'
http://www.members.optusnet.com.au/fischermk/index.htm
Last edited by tfb : 02-23-2007 at 07:38 PM.
 
Final outcome.

It seems my bike likes 1 3/4 turns out on all four of the pilot mixture screws.
Took it out on a 120 mile run today, and it did great. No loading up, no running lean.
After it cools I'll check plug color.

Thanks to all for the assitance!
Hopefully I can repay, and pay it forward.
 
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