How do I adjust the idle on a schebler carb?

[NL967A]

I'm sure it's a simple adjustment but I'm idling a little to fast. Butterfly valve is closed as far as it will go. How do I slow her up?

[T. Cotten]

NL967A!

Is this an HX, or DLX Schebler?

.....Cotten

[NL967A]

Hello Mr. Cotton
I have an H model. To be specific it's and H 111 (I think)!

"Ask and it shall be given to you"

[NL967A]

Sorry Cotten

[T. Cotten]

NL967A!

The idle is controlled by the large screw through the side (1), with a screw above it (2) that seats a friction pad to hold it firm.
Loosen the small screw, adjust the large one, and snug the small one.

Of course, the adjustable needle will affect mixture, and therefor idle speed as well, and it will vary with the adjustments of the throttlecam, so you will probably need to go back and forth between them until you find a 'sweet spot' where the mixture produces its quickest idle before you trim it down with the idle screw.

Unfortunately, many of these veterans have borewear that allows extra air, and the idle screw may not stall the motor when completely screwed in.
Ideally, there should only be "daylight" at the end of the idle screw when the disc is fully closed. (Arrow points at additional airgap from a poorly fitted disc.)

....Cotten

[NL967A]

Hello Mr. Cotten
Thank you very much. I need to turn in my idle screw for sure from what you said. I like where my mixture screw is set so I'll play with the carb a little and hopefully get her to idle down a little. What can you tell me about the adjustment lever on the top of the carb?

[DanM]

If you look at that lever, when you move it from 1 to 3, it changes the cam- the strip of metal the lift lever rides on. You will see how the positions let the roller or nose of the liver in or out, which in turn raises or drops the needle a bit.

The lever will affect the lift lever mostly at idle, but that strip acts as a cam, so there is affect across a range.

For example, if the engine runs fine at mid or upper throttle, you don't turn the needle itself, but use that little top lever to help at the low speed. 1 is leaner, 3 is richer- clockwise 1 to 3 from the top.

[T. Cotten]

NL967A!

Does your assembly have a cam like the first attachment, or the second?

Please note that the three position lever moves the cam in the half-open to full open range.
The idle range is either un-adjustable, such as the first, or adjustable with a screw that flexes the cam (1), and locked with another snubber screw (2)

Turning this adjustor inward would richen the mixture by raising the needle, backing it out would lean the mixture by limiting the needle lift.

....Cotten

[DanM]

Thanks Tom for correcting my post. So, we use the needle valve to set the idle and trim the top end performance with the lever.

Dan

[T. Cotten]

With luck, Dan!

As I posted, will take refinements of the idle screw, needle valve, and the cam adjustor screw, if it has one.
Some models had no dial with a lever, only a second cam adjustor screw for the top end. (attached)

And good luck that the cam is not badly worn, bent, or fatigued.
Beryllium spring sheet stock is incredibly expensive, so if anyone knows of a source of small quantities, I would appreciate the link.

....Cotten

[NL967A]

Hello Mr. Cotten
My adjuster on the top is like your second photo. I've done the fine turning as you suggested and now my 1920 HD J is running unbelievably great! Thanks for your help. I could use a new float bowl gasket. Can you give me a couple leads? Thanks

[T. Cotten]

NL967A!

The literature doesn't indicate a gasket, so you want one as thin as possible to avoid altering the float height.
Fickau Prototypes produces some of the bowl sizes in cork. (Others I must produce from paper for my own services only.)

....Cotten

[2camtom]

With luck, Dan!

As I posted, will take refinements of the idle screw, needle valve, and the cam adjustor screw, if it has one.
Some models had no dial with a lever, only a second cam adjustor screw for the top end. (attached)

And good luck that the cam is not badly worn, bent, or fatigued.
Beryllium spring sheet stock is incredibly expensive, so if anyone knows of a source of small quantities, I would appreciate the link.

....Cotten

Hello Cotten

Is this what You are looking for? Got them NOS.

[T. Cotten]

Looks great, 2camTom!

Please email me direct at libertynightshift@gmail.com, or meet me at D-port?

...Cotten
PS: Ultimately, I will still need beryllium spring sheet, as the cams varied.