What makes the choke close on cold start ?

[maestro7879]

I'm confused on what makes a choke close on a Weber 9665s carb. This carb has a diaphragm pull off with a bimetallic automatic choke. No electric here.

How does the choke close on initial startup ?

My guesses -

1- Done by moving the throttle forward but I can't find what is missing.
2- Bimetallic automatic choke keeps it closed when cold. Maybe I need to clean or adjust?

The engine will start and run great if I manually close the choke and start. The choke will then open up as the coil heats up.

http://www-alt.mercurymarine.com/mnetdata/SERVICE/CRUISER/Servmanl/18/18covr2.pdf

 

[Don S]

Re: What makes the choke close on cold start ?

It's supposed to be electric, you sure it doesn't just vibrate open after you manually close it. The spring is designed to push the choke closed when cold, then slowly unwind the spring and open the choke as the ignition voltage heats the spring.

 

[maestro7879]

Re: What makes the choke close on cold start ?

It's supposed to be electric, you sure it doesn't just vibrate open after you manually close it. The spring is designed to push the choke closed when cold, then slowly unwind the spring and open the choke as the ignition voltage heats the spring.

It's not electric.

It sounds to me after talking to some other people is that the problem is that when i shift it into neutral/full throttle that should close the choke. It's not doing that.

Is the above true or does the spring do all the work ?

 

[Don S]

Re: What makes the choke close on cold start ?

Yours must have the choke stove mounted to the manifold with a link rod going from the stove to the choke, but it's still the same thing. That choke stove when cold is what closes the choke. All opening the throttle does is take the tension off the choke cam so it is free to move. At idle there is pressure on the cam that will prevent it from closing the choke. (NOTE: it's called a choke cam, but it's not a cam like automotive, no steps, it's the same size all around.)

 

[Fishermark]

Re: What makes the choke close on cold start ?

If you have the style that has the divorced choke stove - separate from the carb, on the manifold - you simply bend the choke rod to shorten the rod and make the choke pull closed. Then the engine heat will expand the spring and open the choke. But again, to adjust it, simply bend the rod - making sure it doesn't bind when doing so.