Keihin CV34 idle screw adjustment?

Dumb question, but does turning the screw in (clockwise) make it leaner or richer? I was under the impression that turning it in reduced the amount of air that passed through, thereby making it richer, but reading some threads on here, I think it might be the opposite.

Thanks,
Chris

The idle screw would be that big black thumbscrew underneath carbs 2 and 3. If you mean the pilot screws at the top and to the front of each carb then clockwise (in) is leaner and anticlockwise (out) is richer.

I used to have it ass backwards until Tek9ine set me straight and I double cheked mine

Newb here but also thanks to JR learned that idle adjustment clockwise raises the RPMs.

There are four carbs. Each separate carb has a screw to adjust fuel mixture in its pilot circuit, generally called pilot mixture screw. A small flat blade screw driver is used to turn the screw.

The idle adjustment is a different part, sometimes called idle screw, is a knurled thumb screw which raises or lowers the idle speed setting on all carbs, simultaneously. Usually turned by human fingers. It doesn't affect the fuel mixture.

Here's a carb diagram showing the pilot mixture screw. The knurled idle screw isn't shown on this diagram.

Good Fortune!

[Click on image to enhance view.]

The idle adjustment, sometimes called idle screw, is the knurled thumb screw which raises or lowers the idle speed setting on all carbs, simultaneously. Usually turned by human fingers. It doesn't affect the fuel mixture.

Here's a carb diagram showing the idle screw. The pilot mixture screw isn't shown on this diagram.

Good Fortune!

[Click on image to enhance view.]

I was wondering if there was some sort of base adjustment for that pilot screw? I'm pretty sure from what I've read around people have posted that its 2 screws out. However my screws were all corroded up when I removed them so I did not screw in to see I just took them out. By observation of where the screw sat in the hole, they were way farther adjusted out then only 2 screws from the seated position. I'm confused.

Sorry, lazy use of terminology. I did mean the pilot mixture screws. Thanks for the answer: counterclockwise = richer.

Most of the time on most carbs ---

A pilot screw on engine side of carb is a mixture screw. Turning in clockwise reduces amount of mixture, thereby leaning. And turning out counter-clockwise increases amount of mixture, thereby enrichening.

A pilot screw on air box side of carb is an air screw. Turning in clockwise reduces amount of air, thereby enrichening. And turning out counter-clockwise increases amount of air, thereby leaning.

Good Fortune!

A pilot screw on air box side of carb is an air screw. Turning in clockwise reduces amount of air, thereby enrichening. And turning out counter-clockwise increases amount of air, thereby leaning.

On the Keihin CV34 the pilot screw is on the top on the engine side of the carbs
Turning out enrichens

Spec for the 750/4 is 2 turns but I have found mine work best at 2 1/2 turns out.

I havea set of these carbs but the screws seem to be covered. Anyone have a suggestion for opening this up?

1/8" drill bit to drill through the plug, then thread in a sheet metal screw and pull the plug out with pliers.

Be careful when drilling the plug that you don't jam the drill bit into the mixture screw. It's possible to have the spinning bit run the screw in tight and damage the tip.

Center punch the plug first using a spring loaded center punch. Drill slow with a sharp bit.

After the plug is out, blow out the well with air to remove metal chips before you turn the mixture screw.

The screw itself is about 1/4 below the bottom of the plug. The plug is about 1/8" thick. I can't emphasize enough how important a sharp drill bit is. Never drill fast...always slow and easy.

IF you remove the screws, there will be a spring, a little flat washer and a tiny rubber o ring on it. The washer and O ring often stick in the carb body and have to be retrieved with a pick. Do not blow air through the passage with the screw removed until you have those parts accounted for.

With today's pump gas, it's every common to have to richen up the pilot fuel screws. On many vintage Honda V Twins, we frequently up the pilot jet one size. If you need more than 3.5 turns out to get the pilot mixture correct, you need a larger pilot jet.