can anyone explain how a choke works

[rewdan]

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I am starting to understand how a choke on a mercarb works, as I see it when cold the spring bit holds the butterfly flap on the top of the carb closed under tension, as it warms up from the 12v going through it the butterfly flap is allowed to open....is this right and can I check it by connecting it to my car battery and see if it warms up and 'relaxes'?

 

[robert graham]

Re: can anyone explain how a choke works

If it's working right then the choke butterfly will open as the engine warms up, easy to see. Maybe a little coil spring in there that gets hot and expands and open the choke.

 

[Philster]

Re: can anyone explain how a choke works

Sounds about right. Engine warms = choke opens.

 

[rewdan]

Re: can anyone explain how a choke works

sounds right but if you take the spring bit out and test it on the bench how do you know its working?

 

[rewdan]

Re: can anyone explain how a choke works

the reason I ask is my choke is not doing anything so its broken or needs adjusting but there is no info on this, do I buy a new one or can I test the old one?

 

[Bt Doctur]

Re: can anyone explain how a choke works

Generally speaking, this link might help. http://www.boatfix.com/merc/Servmanl/13/13B5R2.PDF

You remove the electric element ,apply 12v and watch to see if the coil spring moves.

 

[rewdan]

Re: can anyone explain how a choke works

thanks for the link, a bit too general though. I tried applying 12v but the spring didn't move, I was wondering if I should hold it slightly wound under tension and then apply 12v to see if the spring slackened. As if the spring was holding the butterfly closed when cold but when the spring warmed up the tension in it was released and the butterfly opened. Do you think this is right?

 

[rewdan]

Re: can anyone explain how a choke works

word on the street is that if you get resistence between the front connector and the helix then the choke is working, in warm climates like mine the previous owner may have adjusted the choke to compensate for the heat so it never moved the butterfly

 

[johnny be good]

Re: can anyone explain how a choke works

I am not sure about your carb but on some automobile carbs you have to hit the throttle linkage for the butterfly to snap closed . Just a thought

 

[6meter]

Re: can anyone explain how a choke works

You also need to ground the choke element. It won't do anything with just a 12 volt lead hooked to it. With a test light hooked to ground, stab the choke element, key on, should light. Hook the test light to positive and stab the metal around the element. You need the element to be snug on the carb. With light, says it is grounded. If it does this, chances the element is bad.