pilot screw advice

[casperdog]

Hi, just in the final stages of fine tuning my carbs, could someone please confirm which way I need to adjust to richen / lean up.
I've read some richen when screwed in and some when screwed out.
The bike is a 750K5. I've attached some photos to help identify.
Many thanks
Phil

[K2-K6]

It's a generally true statement that any adjustments on filter side of throttle slide is for air,  so in gives more rich setting....and obviously,  out gives leaner mix for idle setup.

Engine side idle adjust is most usually fuel metering and works opposite to above.

Saying that,  I always have to check when doing different carbs  to see I'm going the right way.

[Nurse Julie]

So Nigel, for peeps like myself who easily forget things, please clarify
On a 400/500/550 do you screw the pilot screw in or out to obtain leaner mix?
Sorry for hijacking your thread Casperdog.

[AshimotoK0]

One exception is the CB450K0 Bomber 14C CV carbs ... see this below .. Clockwise to weaken

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[K2-K6]

It's easy to confuse which way different types go,  I always have to sit and think it through when working on different systems to see exactly what I'm trying to get.

On these air screw type (filter side of throttle slide)   the screw if tightened into fully closed blocks all air,  the engine is then sucking on the idle jet a bit like a drinking straw,  so full rich based on the size of the idle jet number/size.

As you open the air screw then the vacuum on the idle jet starts to go down as you allow more air into that passage.  So you get progressively leaner the more air you allow in via the air screw, until you can't get any more airflow.

That's why if you can't get rich enough or lean enough within about 1/2 turn to 2 turns out, it tells you you need to change the idle fuel jet size.

Also if no response it'll tell you which idle circuit is blocked on which carb.

With systems having screw on engine side of throttle slide, you are usually controlling fuel flow not air, so in for less fuel out for more fuel.

As above,  I end up sitting there working it through in my mind to see if I've got it the right way round.

[K2-K6]

Crossed over with Ash there.

It's a generalisation,  but CV carbs usually fall into fuel metering of Idle screws,  with non CV types being air metering screws.  Hence the switch.

[casperdog]

I always assumed that if the screw was on the filter side of the slide then you screwed in to richen and out to make leaner.
However seem to remember reading on here or somewhere else that the opposite is true if these types of screw (1st picture in op) are fitted..ie with holes in....Did I dream this.?
Cheers
Phil

[MarkCR750]

You could be confusing this with info for PD carbs, these have a “fuel screw” , it’s on the engine side of the slide, unscrew give more fuel, screw in gives less fuel, your carbs have the “air screw” on the filter side of the slide, screw in means more fuel, screw out means less fuel.