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Veteran
Posts: 214
| I'm working on a Carter BB single barrel carburetor. When I adjust the idle mixture screw in, the car stumbles and loses RPM's, then the idle speed increases when I begin to turn it out. I keep turning it out 3 -4 turns and the idle stays the same and never loses RPM's. I can almost remove the screw. I know that the idle screw turned out should start to lower the idle speed and then you turn it in again to find the highest idle. So, what could be causing this only when I turn the screw out? Thanks, Nick |
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Board Moderator & Exner Expert 10K+
Posts: 13045
   
Location: Southern Sweden - Sturkö island | Standard procedure is to very carefully screw the idle mixture until it bottons (asolutely no force) and then back off 1-1,5 turns. This can be done with the engine off. With this setting all Engines will idle, then it's just a matter to find the correct setting.
If the idle never changes, then most probably the idle speed screw is set too high and that results in that the throttle valves doesn't close. |
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Expert 5K+
Posts: 8443
Location: Perth Australia | Yeah Nick, the idle screw is just a tapered needle, once you loosen it so far, it wont make any difference
Set as Wiz said
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Veteran
Posts: 214
| I thought that typically the RPM's get lower when you turn the screw in either direction and then there is a sweet spot in between those two points where the idle faulters. Nick |
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Board Moderator & Exner Expert 10K+
Posts: 13045
Location: Southern Sweden - Sturkö island | Yes Nick, but if the idle speed screw is set to high, then you'll never notice it in outward turns, only in inwards turns |
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Veteran
Posts: 214
| Oh ok. I'll try it with a lower idle setting.
Thank you everyone. Nick |
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idle mixture problem
