Missing idle mixture stops
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Joined: Oct 2010
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Missing idle mixture stops
Just getting ready to set up my MC2100 after rebuild, and I noticed that I don't have the stops for the idle mixture screws that hit the power valve cover.
The procedure says to thread the screws all the way in until they seat then back them out 1-1/2 turns. I've done this, and you can see the needles sticking out into the carb throats. Is this right? Or is this assuming that the stops are in place?
When I took the needles out, one was only threaded in 3 turns, and the other was only threaded in 4 turns. Not 3 and 4 from seated, 3 and 4 from falling out. Want to make sure I'm setting this up right. I have half a mind just to thread them both in about 4 turns and start from there instead of all the way in then back out 1-1/2. The truck was running reasonably well before the rebuild.
-MK
The procedure says to thread the screws all the way in until they seat then back them out 1-1/2 turns. I've done this, and you can see the needles sticking out into the carb throats. Is this right? Or is this assuming that the stops are in place?
When I took the needles out, one was only threaded in 3 turns, and the other was only threaded in 4 turns. Not 3 and 4 from seated, 3 and 4 from falling out. Want to make sure I'm setting this up right. I have half a mind just to thread them both in about 4 turns and start from there instead of all the way in then back out 1-1/2. The truck was running reasonably well before the rebuild.
-MK
Hotshot
Joined: Apr 2009
Posts: 14,333
Likes: 247
From: Stanley, VA
The idle stops were there as part of the emission controls. With the stops in place, once the idle mixture was set it couldn't be changed. This was considered part of the "tamper proof" set up that the goverment mandated for the system.
In reality, they were easy to pop off and tamper proof wasn't so much.
You don't need the caps for proper operation.
Initially set the idle like you did. 1-1/2 turns out from seated. Then once warmed up set the mixture for smoothest idle, or if you're using a vacuum gauge, set the idle mixture for highest vacuum reading and forget about the limiter caps, they're unnecessary.
In reality, they were easy to pop off and tamper proof wasn't so much.
You don't need the caps for proper operation.
Initially set the idle like you did. 1-1/2 turns out from seated. Then once warmed up set the mixture for smoothest idle, or if you're using a vacuum gauge, set the idle mixture for highest vacuum reading and forget about the limiter caps, they're unnecessary.
MSEE
Joined: Apr 2004
Posts: 10,386
Likes: 35
From: Austin, TX
Yep, that's normal. This is how the fuel mixture is metered prior to entering the combustion stream.
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