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Manual Choke conversion question.

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GriffinNC Dennis D
Greenville, SC, USA   USA
I’m still struggling with what I think is the choke hanging open. I can adjust it up to about 1800 rpm, but it never will kick down to lower idle speed. Tap the gas etc it will just sit at the high light idle. I have to turn it down with the springed/high idle screw and it doesn’t run bad when it’s warmed up and I can usually start it right up even cold. Blessing of living in the south.

When apart the needle seems to hang very slightly when it’s in the warm position (needle all the way in the tube). At least I believe that is the position it should be in with the engine warm. My guess at the moment is that the needle is staying in that position and not coming out when you depress rhe throttle.

I’am thinking of maybe moving to a manual choke or though. I have seen two versions. Is the one that seems better? Will the manual choke be able to move the needle? Or is it still reliant on the kick piston and little spring inside to move the needle?

Why I’m thinking of it what is the purpose of the kick piston? The large thermal coil is responsible for returning the needle, is the kick piston what pulls it out?

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Falkon Al Martin
Appleton, WI, USA   USA
What needle? Do you have a factory Stromberg carb? These use an enrichment device, not a choke as such. The farther it is turned the more gas it allows into the carb. This PDF shows both the Manual and Automatic "choke".


http://www.marineengine.com/parts/technical_information/sierra_18-7085.pdf



Edited 1 time(s). Last edit at 2019-03-14 05:51 PM by Falkon.

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GriffinNC Dennis D
Greenville, SC, USA   USA
Yes it the original auto choke on the 78 Spit with the Stromberg. The best I can tell is the enrichment needle might be getting hung just where the small o-ring seals as it goes all the way in. I what I do know is it doesn’t seems to want to idle down as it warms up.

I’m hoping to try and pull the water housing and try to operate it manually tomorrow or Sat to see I how it’s functioning. What I’m now sure of is what actually Pulls the enrichment needle down into the tube. The kick piston or the thermal coil. Maybe neither and I’m not picturing it right.

If I change to manual choke does it eliminate the kick piston and thermal coil?

Anyone have a set of directions in pdf for a conversion kit I can read through.

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DerbyRam54 Neville Wardle
Branford, CT, USA   USA
The vacuum kick piston acts on the enrichment needle to reduce the amount of enrichment once the engine has started (but not warmed up) to prevent excessive enrichment. Eventually the thermal spring will push the needle all the way home, but the initial movement is provided by the vacuum piston.

John Twist has a series of YouTube videos on the autostarter, part 1 is at part 2 is and part 3 is

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GriffinNC Dennis D
Greenville, SC, USA   USA
Ok, Good to know.

Since I'm pretty sure my enrichment needle if getting hung in the tube somehow. I've torn it apart a couple times and it's never been quite as smooth as I think it should be. I'm back to the original thought, if a manual choke will eliminate it getting stuck in there. It doesn't take much to get it move, I'm just not sure the springs are strong enough to do it.

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