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Old 02-23-2013, 08:13 AM   #1
pizellu OP
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R1100 gs throttle body mixture screws

Hi everyone, just bought an 1100gs, and was wondering
How much turns should the mixture screws on the throttle bodies
Be out? My gs is having a hard time starting, and wasn't wirking good at all.
Furst it was back firing , then i put the screws 2 1/2 turns out and it is better now but still is stuttering when i drive it!!! Any help would be appreciated ;)
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Old 02-23-2013, 08:21 AM   #2
mouthfulloflake
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they are called "BBS"

big brass screws, or something like that.

start here

http://advwisdom.hogranch.com/Wisdom/

or here, the BBS are referred to in these articles.

page 13 of this one ----> http://advwisdom.hogranch.com/Wisdom/TBS4Dv1.0.pdf

http://www.ibmwr.org/r-tech/oilheads...bod_sync.shtml
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Old 02-23-2013, 10:31 AM   #3
slartidbartfast
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They are not really mixture screws.

What do you know of the bike's history?

I'd start by putting the screws back where they were and running a full tank of clean gas through the bike with a bottle of injector cleaner in it.

Read up on the valve adjust and throttle-body synch procedure in the Hall of Wisdom (see link provided above or at the very bottom of the page). If you don't know the bike's history, you should plan on doing those maintenance items along with oil changes, check the air filter, change the plugs, and then see how its running. Longer term, you might think about changing the fuel filter and internal hoses in the fuel tank and cleaning the injectors.

Mechanically, apart from normal maintenance items and a careful check of swingarm and final drive bearings, replacing the brake hoses is probably the only thing you need to consider right away.
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Old 02-23-2013, 11:22 AM   #4
def
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Quote:
Originally Posted by slartidbartfast View Post
They are not really mixture screws.

What do you know of the bike's history?

I'd start by putting the screws back where they were and running a full tank of clean gas through the bike with a bottle of injector cleaner in it.

Read up on the valve adjust and throttle-body synch procedure in the Hall of Wisdom (see link provided above or at the very bottom of the page). If you don't know the bike's history, you should plan on doing those maintenance items along with oil changes, check the air filter, change the plugs, and then see how its running. Longer term, you might think about changing the fuel filter and internal hoses in the fuel tank and cleaning the injectors.

Mechanically, apart from normal maintenance items and a careful check of swingarm and final drive bearings, replacing the brake hoses is probably the only thing you need to consider right away.
Well, realistically, they are mixture screws in that these screws control the amount of air by-passed around the throttle plates at idle. The amount of air by-passed controls the idle air/fuel mixture and tip in throttle response. The fuel delivered at idle is considered to be constant (controlled by the Motronic) and therefore, idle mixture (and idle RPM) is adjusted by these screws. In my experience, the idle by-pass screws (BBS) have no affect on engine performance once the engine is off idle.

Here is the reference from my REPROM (2001 GS)

Adjust idle speed by turning the air bypass
screws while checking that the carburettors are
balanced.
Idle speed: .......................................1,100 50 rpm


Note the reference to carburetors. The engine is fitted with fuel injection throttle bodies not carburetors. The technical writers got it a bit incorrect.

As for BBS initial settings, those on my model (2001) are at ~1 1/2 turns from seated.
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Old 02-24-2013, 10:49 AM   #5
pizellu OP
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Bbs turns

Well at 1 1/2 turns the bike works pretty bad, and smells of petrol! I have ordered a carb sync to tune the throttle bodies first and see how it goes. Funny thing is one day worked fine, and the day after works rubbish !!!??!
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Old 02-24-2013, 11:13 AM   #6
Pekkavee
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Have you checked the throttle cables. If the throttle cable is stuck in the right hand side it means a lot of trouble. Like this.



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