Air mixture screw?

[tdan553527]

Mine is at 2.5 turns out, question is, does going out make it leaner or richer?

[suzukimad]

I think it makes it richer

[tdan553527]

Thank you  

[vfrocket]

yes the more turns out from all the way in make it progressivly leaner... ie 4 turns in richer than 2.5 turns....

[tdan553527]

SCORE 1-1

[cummuterguy]

the mixture screw blocks fuel flow. so the further in it goes, the less fuel can get past it.
unscrew for richer, (counterclockwise)
screw back in for leaner (clockwise)

[Jake D]

Thump!

(sound of dizzy head hitting desk).

[ConanLloyd]

So let me get this straight.....

In order to do the Srinath "3 turns out" we tighten it all the way in, then back it 3 turns out.

Is that correct? :dunno:

[cummuterguy]

correct... then from there, if you feel it's still too lean, you back it out some more, if it's too rich, you screw it in a bit

[gp]

from a new rider's perspective,
how do we know whether its too lean or too rich??
how can we tell?  

thanks heaps,
gp

[gs500ey]

Well I'm actually messing around with that the last two days, really annyoying since I dont have a carb adjusting tool, so i'm using a flathead screwdriver bit.

My symptoms was that when driving say from 15 miles faster to a stop, the engine would cut out. As long as i kept the throttle turned and rpms above like 2K it didnt die. Coming to a stop i tried pulling the choke and it seemed to help.

So today I turned the carbs counterclockwise (richer) about 3/4 turn on each side and i seemed to have a couple pops/backfire. So i stopped and turned it in clockwise (leaner) like probably more than 3/4 turn; however it didnt make any backfire it did die when coming to a stop.

Turned it out (leaner) like 1 turn and I guess I'm where I started.

If it backfires you most likely it is running lean, it is also a possibility that it is running rich and the carb is getting flooded and stalls. However if that was the case for me, putting on the choke wouldn't have helped.

[GeeP]

There's a little terminology involved here.

There are two forms of idle mixture control:

1)  Idle air "pilot air"

2)  Idle mixture

Idle air screws adjust the idle jet emulsion rate.  They let air into the metering system, and more air means less fuel.  Therefore, turning the adjustment clockwise enriches the mixture, turning counterclockwise leans it.

Idle mixture screws adjust the mixture directly.  Idle mixture screws have a needle valve on the end that directly limits the fuel flow.  Turning clockwise leans the mixture, turning counter-clockwise enriches it.

As far as adjustment is concerned, the best way is by feel and sound.  Start at a predetermined setting (2.5 turns from closed on the GS).  Start the engine and slowly close one or other of the air screws.  As the mixture gets richer the engine will start to labor, the exhaust note getting a little deeper.  Now turn it out slowly.  As the mixture gets leaner you'll notice the engine RPM increase slightly, then drop off.  Going even leaner, the engine will start to misfire and stumble.  The exhaust note will also sound a little more hollow.

The correct mixture setting is just rich of peak RPM.  Once both carbs have been roughly set, go back and re-peak the first carb.  Then the second again.  This is just for accuracy, as it can be difficult to be precise when one carb is out of tune. 

[Egaeus]

There's a little terminology involved here.

There are two forms of idle mixture control:

1)  Idle air "pilot air"

2)  Idle mixture

Idle air screws adjust the idle jet emulsion rate.  They let air into the metering system, and more air means less fuel.  Therefore, turning the adjustment clockwise enriches the mixture, turning counterclockwise leans it.

Idle mixture screws adjust the mixture directly.  Idle mixture screws have a needle valve on the end that directly limits the fuel flow.  Turning clockwise leans the mixture, turning counter-clockwise enriches it.

As far as adjustment is concerned, the best way is by feel and sound.  Start at a predetermined setting (2.5 turns from closed on the GS).  Start the engine and slowly close one or other of the air screws.  As the mixture gets richer the engine will start to labor, the exhaust note getting a little deeper.  Now turn it out slowly.  As the mixture gets leaner you'll notice the engine RPM increase slightly, then drop off.  Going even leaner, the engine will start to misfire and stumble.  The exhaust note will also sound a little more hollow.

The correct mixture setting is just rich of peak RPM.  Once both carbs have been roughly set, go back and re-peak the first carb.  Then the second again.  This is just for accuracy, as it can be difficult to be precise when one carb is out of tune. 

I was told by a friend that by using a vacuum gauge, you should adjust the screw for maximum vacuum as that is the most efficient combustion.  Since you seem to be pretty good with carbs, I was wondering if you agreed.

[GeeP]

That's correct.  Venturi suction will rise with RPM.  You might be able to use suction available at the slide valve vacuum cap to effect a reliable adjustment, but I haven't tried.

[mjm]

My symptoms was that when driving say from 15 miles faster to a stop, the engine would cut out. As long as i kept the throttle turned and rpms above like 2K it didnt die. Coming to a stop i tried pulling the choke and it seemed to help.

So today I turned the carbs counterclockwise (richer) about 3/4 turn on each side and i seemed to have a couple pops/backfire. So i stopped and turned it in clockwise (leaner) like probably more than 3/4 turn; however it didnt make any backfire it did die when coming to a stop.

Turned it out (leaner) like 1 turn and I guess I'm where I started.

On my GS out = richer.  You should check a few things -

1 - what is your idle RPM when fully warmed up?  Set it to about 1200 ` 1500 after a 15 minute or so ride.  You said that putting the choke on helped the problem - it might be that you are turning it off "too soon" The choke on the GS opens an  extra fuel passageway and richens the mixture - leading me to believe that the bike is either below operating full temperature on a short ride, has the idle set too low or is lean.

2 - check that float level is approximately equal to the gasket surface between the bottom of the carb (the bowl) and the main body.  You can check this with a small piece of clear fuel line, the bike not running, the petcock in "prime" and all parts on the bike - a search should find the method.  An improperly set float level can flood/starve the engine under braking.

3 - Most GS's run better at around 3 turns out from lightly bottomed

4. InstaLL one size larger pilot jets - ALL YEARS (40is the size for all before 2001, 20 for those after) which will improve cold starting and idle at the expense of a little pollution.