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Mixture screw on Carb

I'm wondering if anyone could tell me where I can find the mixture adjustment screw on my Mikuni BSR 33. I can't find it.

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I believe it is near the bottom, around where the float bowl meets the carb body.. You need a straight small screwdriver (Short) facing upward.

Posted on Jul 29, 2009


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What is the proper adjustment for the idle fuel mixture screw located on the bottom of the 32mm mikuni carb on the 07 yamaha royal star?

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Hi, Anonymous the carburetor throttle shaft wheel has two cables the cable closest to the right side of the bike is the throttle cable and the one closest to the left side is the idle cable. Right about the middle between the two is the idle adjustment bolt it faces out towards the air filter end of the carb. The engine should be at operating temperature with the enrichener off to set the idle between 950-1050 rpm. Turn the idle adjustment bolt clockwise to increases idle speed and counterclockwise to decrease idle speed. If you have access to your air fuel mixture bolt you may adjust it as well if not there is a video below on how to gain access, make sure you start with clean or new spark plugs. Gently turn the air fuel mixture bolt clockwise until it starts to bottom out "STOP" do not over tighten as it will damage the taper on the end, now back it out 2 full turns to establish a starting point start the engine and check the idle rpm's and adjust the idle adjustment bolt accordingly for 950-1050 rpm if necessary, adjust the air fuel mixture bolt 1/4 turn at a time and let the engine settle for about 10 seconds, clockwise for a leaner mixture and counterclockwise for a richer mixture you are seeking the highest rpm your air fuel mixture bolt can acquire without going past 3 full turns from bottom then readjusting the idle adjustment bolt back down to 950-1050 rpm If you can not detect any rpm change and can not stall the engine by turning the air-fuel mixture bolt all the way in then your pilot/low-speed jet is too big. Final adjustment should be made with a clean air filter mounted to the carburetor. For more information about your issue and valuable "FREE" downloads that you will need please click on the blue links below. Good luck and have wonderful a day.
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I am trying to tune the carb on a Yamaha 80 raptor. I do not know which screw does what. By the way, this is NOT a G5. It is a small 4 wheeler The carb is a Mikuni G499? or a 5TH1.00? HELP Please !!!!!!

On most Mikuni carbs The screw that lines up with the middle of the slide and often has a spring on its shaft to stop it moving is the idle screw, it merely lifts the slide to increase engine revs, the same as opening the throttle and will not change mixture or jetting.

The smaller screw often on an angle, or from underneath is the mixture or air screw. this will affect mixture mainly at idle, low revs, starting.
these are usually set by screwing it all the way in and counting the turns, then back it out the same number of turns to get a start point, usually about 2 turns out from the fully in position. it should only need adjusting about a quarter of a turn either way.

with the bike idling as you turn it in, the engine will start to bog down (rich) as you screw it out the engine should smooth out until it has an uneven idle and change in idle speed up and down(lean) and pick the smoothest idle in the middle, but this should be less than 1 turn from rich to lean

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