Air/fuel mixture Back fire I need to know the stock settings for the mixture screw

Hi there. The ''default'' settings are :
step #1 turn the mixture and idle screw all the way in clockwise
step #2 you turn counter clockwise the mixture screw for 1,5 rounds, and the idle screw when the motor can run freely without going off.
#3 Then you adjust the mixture screw if you do not like the outcome by micro movements clockwise. Hope i helped.

The carb mixture screw may add air or fuel, depending on the model. If the bike will idle it can be adjusted without knowing the factory setting. What you want is the highest idle that can be achieved using just the mixture screw, not the idle setting screw. Start the motor, then slowly turn the mixture screw in. If the idle speed increases, continue in that direction. If it slows and becomes rough, turn the screw back out until you reach the highest idle speed. That will the correct setting for the bike at your altitude.

Sounds like your fuel air mixture is a little rich. Check your plugs, if they are black you are running rich which will cause some of the excess fuel to be burned off in your exhaust. Two common problems with a bikes fuel air mixture is bad plugs, if one does not fire consistently all the time it will leave excess fuel in the combustion chamber. Another would be a clogged air filter keeping the fuel air mixture unbalanced as well.

Lastly if you are able to, you may adjust your air fuel screws on your carb. However most Honda's are stock with Keihin carburetors and these air fuel screws are plugged so you cannot make adjustments without drilling out the plugs.

the carburetor settings are easy : 1- locate the screw mixture air /fuel 2- wind the screw all the way in 3- unwind the screw 1 1/2 turn and this should be sufficient to set the carburetor back to its original settings for the air/fuel mixture . 4- as for the idling screw , wind it down to suit the revs required

15:1 fuel air ratio is considered best in most applications. Too lean runs hot, too rich fouls.

Here are some images that might help to assist you, and let me know if you require any further assistance.


Adjust the curb idle with the engine warmed up and the choke off.




The air/fuel mixture screws should be adjusted with the engine warmed up and at normal idle speed, then turn each air/fuel mixture screw in one at a time until the engine just begins to mis-fire, then back the air/fuel mixture screw out 1-1/2 to 2 turns out a half a turn at a time until the engine idle is the smoothest. (your vehicle might have restrictor caps over the air/fuel mixture screws to limit the amount of adjustment)






The choke adjustments;






To adjust the vacuum tension pull on the choke pull-off:





Adjust the fast idle screw to the proper RPM with the engine cold and the choke on.

LIGHTLY seat both the throttle screw and air screw. Now back each one outward one and one half turns. This is the stock setting.

Could you take a moment and rate my answer? Thanks!

Carb.basic setting.
On the Carb to Intake manifold there is an AIR/FUEL volume control screw. Gently screw it in Clockwise until it bottoms out, then back it out 2 turns.
Next, find the Throttle Butterfly Fast/ Slow idling screw, and back it out until the Throttle linkage is released.
Then slowly wind it back in 2 turns
If you have SPARK and FUEL up, then it should Fire Up.
When it does, using the Air/Fuel screw to stabilise the idle mixture, adjust the Idling Speed Screw to run balanced at around 750 RPM.
Happiness!!!
All the best and Regards, DT