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I need to know how to set the air fuel screw - OMC Carbrators

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I have tryed to holter air fule mixture no joy what are the 3 screews


Depends on the type of carb.
One screw is likely to be the throttle stop screw used mostly to adjust the idle speed but sometimes only to provide a basic setting for the throttle.
One screw is likely to be the idle mixture fuel adjustment screw. Although primarily for setting the idle mixture it can influence running to almost a quarter throttle.
The third screw could be either a fuel screw or an air screw. An air screw tends to be significantly larger than a fuel screw and would be used to set the idle speed after the basic setting of the throttle stop.

If a fuel screw it could be intended to provide adjustment for part load.

There is a large difference in the way carbs of different designs need to be dealt with and adjusted so referring to the manual is very important.
Changing the air/fuel ratio at the wider throttle openings (and getting it right) generally needs much more than turning screws and can involve slides and springs, jets and needles and an experience level that to the uninitiated seems akin to the black arts.

It is a general rule, incidentally, that before tackling any suspected carb problems everything else should be put into specification order, particularly all the engine timings, valve clearances, ignition system and intake and exhaust breathing.

Aug 22, 2015 | Motorcycles

1 Answer

How to adjust the fuel and air mixture on a 1982 ford 4.9 six cylinder, carter carburetor.


There should only be 1 screw located at the base of the carb facing outward.

The method I use requires a tachometer. If you don't have a tachometer then you can use the "by ear" method, though it's not as accurate.

With the engine off, start by turning the screw all the way in, then back it out 1 and 1/2 turns. This usually give you a baseline to start with.

Start the engine and get it up to operating temperature, make sure the choke is fully open, and have the air cleaner and all vacuum lines installed.

Using the tachometer (or ear) turn the screw (usually out) until the RPMs increase. If they don't increase by turning the screw out, then try turning it in.

Eventually the RPMs will stop climbing while turning the screw (as said earlier, usually out).

THEN turn the screw the opposite direction (usually in) until the RPMs JUST start to drop off. That should be real close to the optimum setting.

This setting is ONLY for the base idle air/fuel mixture and is NOT for anything else.

Hope this helps.

Feb 16, 2015 | 1982 Ford F 150

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Honda gx160


Kescorpio56:
Check your throttle and choke settings. Something is causing the throttle plate in the carburetor to remain open or the governor is improperly set. I would reset the air/fuel mixture screws to one and a quarter turns out and back the idle screw all the way out. Make sure that the throttle cable operates the throttle properly and check the governor setting and reset the governor setting if needed. Start the engine and adjust from there. When the engine starts, adjust the idle screw until the engine idles. Adjust the fuel/air mixture screws for the best idle. Then run the RPM up and adjust the fuel/air mixture screws for the best run/idle combination. Don't forget to adjust the governor if the engine runs too fast or too slowly.

May 31, 2013 | Air Tools & Compressors

1 Answer

My yz250 uses way to much fuel and spits oil even with a 50/50 ratio. I dont know if i need to change the jetting or adjust the air screw.


Probably both settings need attention. But you could have a sticking carb float too. Here is a pretty good procedure for setting air to fuel mix:

http://bikeadvice.in/tuning-carburetor-optimal-performance-fuel-efficiency/



If performance still lacks after adjusting dismantle and inspect carb.

Dec 21, 2012 | Motorcycles

1 Answer

Idle set 2004 fxdwg


Hi Anonymous, on the right hand side of the carburator there is an idle adjusting screw with a spring behind it, turn screw clockwise to increase idle counter clockwise to decrease idle. There is also an air/fuel mixture screw inside a carb body lug that may or may not be plugged with an aluminum cap that's about 3/16" thick. This cap can be drilled out to acess the air/fuel mixture screw. Turning screw clockwise will lean out mixture and lower idle, turning screw counter clockwise will richen mixture and raise idle. You need to balance the two adjusting screws to obtain an idle of 950-1000 RPM then back out air/fuel mixture screw 1/4 turn, snap throttle to confirm responce, you may continue to back out air/fuel mixture screw untill desired throttle responce is achieved, if you see black smoke coming out of exhaust you have gone to far and need to turn screw back in 1/8 turn at a time, final adjustment should be made with the engine at normal operating temperature. Good luck and hace nice day.

Feb 26, 2012 | Harley Davidson FXDWG - FXDWGI Dyna Wide...

1 Answer

How to ajust carb on a harley 1100 sportster need to know settings bike is jumps in 1 st & 2 nd gear after 2 nd runs good


Hi Deeprun5, on the right hand side of the carburator there is an idle adjusting screw with a spring behind it, turn screw clockwise to increase idle counter clockwise to decrease idle. There is also an air/fuel mixture screw inside a carb body lug that may or may not be plugged with an aluminum cap that's about 3/16" thick. This cap can be drilled out to acess the air/fuel mixture screw. Turning screw clockwise will lean out mixture and lower idle, turning screw counter clockwise will richen mixture and raise idle. You need to balance the two adjusting screws to obtain an idle of 950-1000 RPM then back out air/fuel mixture screw 1/4 turn, snap throttle to confirm responce, you may continue to back out air/fuel mixture screw untill desired throttle responce is achieved, if you see black smoke coming out of exhaust you have gone to far and need to turn screw back in 1/8 turn at a time, final adjustment should be made with the engine at normal operating temperature. Good luck.

Aug 20, 2011 | Harley Davidson XLH 1000 Sportster...

1 Answer

MY SPARK PLUG FOULSALL THE TIME. BLACK SOOTY ON THE END OF THE PLUG.


Ok most likely cause for this is jetting (Carbi) and or the air / fuel mix screw set to rich - Well done for noticing though as no where near enough people read their spark plugs and make adjustments - they normally wait til bike don't work before researching?
Simplest and first option would be turn in your air/fuel mix screw quarter to half a turn in (clock wise) this leans the fuel mix slightly
Second option if still not helping from just screw adjustment is put the mix screw back to where it was before and change the pilot jet to a smaller size - the pilot jets have number stamped on them so once you have yours out look for the number and just buy new 1 or 2 sizes smaller (they only about $5 each) then of course go back to fine adjustments on your air/fuel mix screw to find the correct balance
You will very quickly know if your setting is to lean as result of adjustments as you will get back firing when rolling of the throttle if becomes to lean
jetting and air fuel mix adjustments can be annoying sometimes as you may need to go up a bit then down a bit then up again but take your time do very minor adjustments then check results and my tip is only ever change one thing at a time then record the change then test and record the result if you dont you will very quickly forget what you did, not know what to reverse if result was poor and if result was good you won't know exactly what made the improvement.
good luck mate regards Jamie

Jul 03, 2011 | 2003 Honda CRF 150 F

1 Answer

I just need to know the air/fuel mixture screw setting for my suzuki tf 125. screw it all the way in and then how many turns out


HI it is usually 1 to 1.5 turns out depends on the carburetor and how clean all the ventures are (all the air jets)

Sep 28, 2010 | Sport & Outdoor - Others

1 Answer

I have a 1988 polaris indy 650 triple and i need to know the right screw turns for the air and fuel mixture and the high idling screw


The polaris air screw are 1 full turn each for the 650's, used drill bits to set up the carb plunger, 1/8,,1/4. etc.

Feb 23, 2010 | Polaris New Genuine Polaris Snowmobile...

1 Answer

1980 1100, I need mixture screw settings, have set at 2 turns out but am at about 2000ft above sea level so maybe has to be altered slightly? In or out?


First - I do not know this bike specifically, but with 4-strokes the screw usually adjusts the fuel, not the air in the pilot circuit. Keep in mind this screw only adjusts the mixture from idle up to just under half throttle. It won't effect higher engine speed performance.

Basically, you can adjust them in 1/2 turn increments until you get the desired performance. Or, fire it up, and adjust the screws with it idling until you can get the highest, smooth idle - this is likely where it will be best.

Now - if the screws are 'behind' the carb slide (air filter side) they are an air screw. If they are on the engine side of the slide, they are fuel screws - the two work opposite of eachother. They're likely on the engine side of the slide, so screwing them in will lean out the pilot circuit (less fuel). So - if after you adjust the screws as described above, check to see how far out from seat they are. If you are not around 1.5-2.5 turns out, you might consider changing the pilot jets inside the carb.

Nov 12, 2009 | 1983 Suzuki GSX 1100 E

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