Air mixture screw

Is this the air mixture screw?

 

It's a tiny flat head in that hole

 

Which bike do you have?

 

82 xj 750 maxim

 

yes that's the mixture screw for the pilot jet circuit

you want a screw driver that fits tight into the slot .just make sure your screw driver sides also fit into the hole. soak in penetrating oil
kroil is the best penetrating oil . also called aero kroil comes in an orange can ​

 

Perfect thanx, so that's the one I keep reading about that you seat gently then 2.5 turns out, the factory caps were off so they've been screwed with at some point,

 

caps off could also indicate someone knew how to clean carbs. when you get the set for the last time you can replug them with disc or get rubber plugs to keep the crud out
you will end up closer to 2-3/4 to 3 turns out when done tuning

 

How can you tell when it's set correctly and should they all be the same turns out like all 2.75 or all 3

 

by the plug color or get a color tune .

 

If you have a good ear you can tell, but that takes a lot of practice, and results in a failry coarse setting (in the ballpark, but not "perfect").

If you can read a sparkplug for color and heat you can tell. Less practice required, but a bit tedious and relatively slow (but cheap).

If you can do neither then you should invest in a Gunson Colortune. It allows you to see the combustion as it occurs, and adjust the mixture until the burn is correct.

The will not all be at exactly the same number of turns out (but they should be pretty close). The mixture needs to be adjusted in relation to how much vacuum each cylinder is pulling (affecting airflow volume to that cylinder). A very healthy engine will have all the idle mixture screws very close to one another. A very sick engine will result in the opposite.

 

i better go the colour tune way, is there a certain way to do the test or just start at one side and work your way over

 

Most say start at 3 then 4 1 2, the readjust, as you adjust eack cylinder it affects RPM and therefore affects vaccuum on each cylinder, run thru 3 times till all are good to go

 

Ok thanx, sounds easy enough, looking at the prices of these colortune things I'm probably gonna go with the look at the spark plug method, still gotta buy a front tire soon

 

So would this be a good plan of action, spray the screws with penetrating oil turn the screws clockwise and gently seat with proper size flat blade, back them out to 2.5 turns and start with that, go for a ride and see what the spark plugs look like, then adjust screws if need be.

 

A good plan would be to remove them and make sure the o-rings are in good shape, then soft-seat them and set the baseline. That will give you some clue as to how well, and how long ago, the PO cleaned the carbs.

 

Ok I'll ad that to my plan I've taken the carbs out a couple times so I'm getting quicker at it

 

I bought new spark plugs and when I changed them I noticed the 2 on the clutch side had white ashy tips and the 2 on the brake side had black soot on them, so that's another reason I wanted to play with those screws

 

one side to the other

 

cylinders are numbered 1 2 3 4 from left to right as you sit on bike.

which bike are we talking about?