Working on my basket case and trying to understand the otter choke function. Following is my idea of how it works.
1. Otter choke assembly gets fuel from one carb.
2. The long spring loaded needle is normally open allowing fuel into the chamber
3. The otter choke solenoid is normally closed and the piston is held over the vacuum port by a spring which prevents vacuum from pulling fuel into the manifold.
4. The ground wire for the solenoid goes to the thermal switch which is also normally closed.
5. When the key is turned on, the solenoid is activated, lifting up the plunger allowing engine vacuum to pull fuel up past the spring loaded needle and into the manifold.
6. When the engine reaches temperature, the thermal switch opens breaking the ground connection and the solenoid turns off and the spring closes the plunger shutting off vacuum from the manifold and stopping the fuel flow.
I'm unsure how that spring loaded needle works- what pulls it closed?

Thanks for any help

 

Your list looks correct. I believe the needle also moves up & down based on engine vacuum in order to vary the mixture when the auxiliary carb is "on". The needle has an adjustable stop nut limiting downward movement. Here is a good reference..... https://sucarb.co.uk/technical-choke...ary-enrichment.

cheers , Richard

 

Thanks,
I read the article, but there appears to be one line missing and he refers to vacuum as "depression". I can see now that the needle is normally in the full open position and when the car goes to idle and vacuum increases, the vacuum pulls the needle down and reduces the flow, leaning the mixture. However there seems to be no seal around the needle, so it is open to the atmosphere and vacuum would have no effect. The cutaway diagram does not show any seal or o-ring. Hoping to find a photo of the various choke components so I can see if something is missing.

 

UPDATE-
After looking closer, it appears that my main needle has been broken off or filed off some time in the past, so it is not normally open as I thought. Someone in the past had run the adjuster down to the leanest position, but to no avail. All the diagrams show the needle as being pointed on the end, and the way it is now, it would be full rich all the time. Now I need to find a new needle.

 

You are correct, there is no seal around the needle. The disc at the top of the needle is a relatively close fit inside the top bore of the carb. So engine vacuum acts on the disc and needle assembly without a seal. Similar to the full size carb's piston & dashpot. My needle looks similar to yours, so I'm not sure if yours has been modified. Cheers, Richard

 

Richard,
Thank you for the info- it clears up a lot of questions and double thanks if you removed the needle from your carbs to show me the picture.
John