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Electric choke not choking completly


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I've got an issue causing hard cold starts. I don't think my choke is engaging all the way. If I manually choke it while starting it (using two people, or a stick, or something) it always starts right up. The fast idle cam works, but maybe the spring on the fast idle cam doesn't seem strong enough to move the choke back up after sitting for a while. The choke does disengage all the way after warming up.

Here's a video of the choke going from open to closed when the throttle is goosed, and what the free-play looks like.

As always, thank you for your time.



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Depends on the year but earlier ones had 3 screws around the outer black plastic housing. Loosen and turn counter clockwise to set richer.



The later 720s the choke was set and not adjustable. I think this one below was sealed. But...



There was a tab that locked the black plastic choke housing from turning. I just ground the tab away and made it adjustable....


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The choke is controlled solely by a bi-metallic spring under that black cover. When cold it contracts and will pull the choke plate closed. There is an electric heater under it that warms the spring when the engine is running and it unwinds opening the choke. The fast idle cam is pulled up into position by a linkage connected to the choke plate. When the choke opens the fast idle cam is free to drop down out of the way by it's own weight.


The electric heater is timed (about 8 min) to open the choke as fast as the engine warms up. It's efficient, fool proof and saves gas over the manual type.

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The 'spring is mounted inside that black cover. It has a hook shape that has to be hooked over the choke plate arm as it is put in place, then turned left or right to set the amount.




If the choke is the kind that can't be adjusted you will find a small obstruction on the case. Just grind it away so the cover can be turned.

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I took out the two rivets and the phillips screw on the bottom, filed off the tab, and adjusted the choke. The inside of the spring housing was filled with what I can only describe as carbon deposits. Black, crusty, horrible stuff.


I had previously cleaned and lubed everything THOROUGHLY.


Based on one start-warmup cycle I can say the choke works now!

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