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Mixture/Air Screw - Which way to lean?

  • Thread starter Thread starter Anonymous
  • Start date Start date
A

Anonymous

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OK, I've been getting conflicting reports.. so I'm going to the experts now.
FYI - '82 GS750TZ

On my Mikuni Carbs, CV with only the one screw for mixture... some people call it the air screw.

Which way do I turn to make it more lean mixture? I thought it was out (counter clockwise)? Is this right?

The spark plugs seem to be constantly black and sooty and engine has poping when throttle is pressed.
 
On mikuni CV type carburators turning the air bleed screws counter clockwise, (out) will alow more air to pass through leaning the pilot circut.
this will have little to no affect on the main circut.
it controls the mixture at idle and just off idle.
 
Leon stated:
On mikuni CV type carburators turning the air bleed screws counter clockwise, (out) will alow more air to pass through leaning the pilot circut.
this will have little to no affect on the main circut.
it controls the mixture at idle and just off idle.
Click to expand...

So, how does one get the nice brown tips on the plugs, instead of the black sooty plugs I have after 1000 miles of riding?

John
 
The correct answer is: turn them out (counterclockwise) to enrichen,
in (clockwise) to lean.
This applies to mikuni CV carbs with the air or mixture screw on top of the carb between the carb body and engine.

bill
 
So, how does one get the nice brown tips on the plugs, instead of the black sooty plugs I have after 1000 miles of riding?
Click to expand...

The million dollar question! Running lean can be the result of many things- timing, valve setup, seals, exhaust setup, jetting etc. I have recently determined this about the carbs- they are usually less to blame for poor running than I origninally thought. For years I figured that the cause of my rough running bike was carb related, so I rebuilt the carbs. No change in running at all. Mine was an electrical problem in conjuntion with some worn cam seats.

We probably need to know a little more about your bike setup- has it an aftermarket exhaust? Jet kit? Pod filters? Has it had problems charging?
 
Its out to weaken the mixture thats why, its called an air screw. Screw it out, allow more air in its the same for all carbs.
I have to agree it may not be the air screw thats the problem, it could be the wrong plugs, check the numbers, is the choke going off fully, leaky exhaust, start with the easy things and work up from there.

Best of luck Keith S
 
billp said:
The correct answer is: turn them out (counterclockwise) to enrichen,
in (clockwise) to lean.
This applies to mikuni CV carbs with the air or mixture screw on top of the carb between the carb body and engine.

bill
Click to expand...

sorry but turning them out (counterclockwise) will allow more air to pass leaning out the idle mixture, my bike (80 GS1000G) was lean at idle and slightly lean running at road speed, turning the air bleed screws in a quarter turn corrected the leanness.
 
Thanks guys, I'll put the carbtune on it, lean the screws out a bit, and carbtune again to see if this helps some of the problems I'm seeing....

Man, I love this site.

Happy/Safe Riding!
 
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