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Discussion Starter #1 (Edited)
On my 4100, the old pin that goes through the fast idle screw clamp was wobbly worn down. I replaced it with a new, all-metal one. Now my throttle plates won't close all the way. It looks like the problem is the pin bumps up against the bird's mouth of the secondary.
When I remove the pin the plates will close a little more before the clamp bumps up against the carburetor housing. At that point though, only one idle hole is exposed, which is what I want but the tolerance seems pretty small, like maybe the throttle is off a click. I can probably live with it though.
My question is mostly about the pin. Leave it out, sand it down, replace it with a thin screw (looks like what was on there), make some other adjustment...?

fast idle screw.jpg
 

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i ran into this a long time ago. IIR, theres more than one fast idle arm, and you have the wrong one. the orig. one had a plastic pin which held the screw from turning from vibration
 

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Discussion Starter #3
I see it is called the Secondary Stop Pin, the plastic replacement costs more than I want, really. Maybe I'll just grind the one I've got till it clears the bird's mouth.
4100 secondary stop pin.jpg

I'm still puzzled at how the throttle plates won't close all the way (to the lowest idle fuel hole). Does that seem normal?
 

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Discussion Starter #4
I've grinded the secondary stop pin down to where it is quite thin but still it won't get past the birds mouth lever so the throttle can close a little more. And the fast idle screw needs to be in almost all the way just to contact the cam. It is as if the bracket for the screw and pin has shifted back a half inch.
 

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Discussion Starter #6
What is the "fast idle arm" , please describe.
 

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Discussion Starter #8
The diagrams show that is the Fast idle adjusting screw. Are you saying there are two part numbers for that piece and I have the wrong one?
One of the numbers is 9538, what is the other one? What's the difference?
Thx
 
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