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| | | | Joined: Sep 2018 Posts: 17 New Guy | | New Guy Joined: Sep 2018 Posts: 17 | I have a 1954 big bolt with a yf2100s carb. All the passage way are clear. I just bought the truck. It doesn't matter where the idle mixture screw is set, all the way in or completely removed. the engine runs the same. The previous owner "rebuilt it". When I removed it there was no gasket. It has 2 holes on the bottom surface. one under the mixer screw and one opposite of it. The one not under the mixer screw lines up with a groove in the manifold. I made a gasket with a groove for the hole under the mixer screw. The engine seems to run rich all of the time now. Before I made this change, the engine ran better when the brakes were applied. I know I have a hydrovac problem. I will get to that. What is the deal with the carb. The mixer screw had no affect before or after the gasket. Like I said before, as far as I can tell, all passages are open. | | | | | Joined: Nov 2002 Posts: 2,766 Carburetion specialist | | Carburetion specialist Joined: Nov 2002 Posts: 2,766 | If the throttle positioner screw is turned in (clockwise) too far; then any adjustment of the idle mixture control screw from seated to removed in your pocket will make no difference, as there is insufficient throttle velocity to activate the idle circuit.
TRY:
(1) Lightly seat the idle mixture screw
(2) Back out the idle mixture screw 1 1/4 turns
(3) Start the engine, and run until at normal operating temperature
(4) Use the throttle positioner screw to adjust the idle RPM to spec
Adjusting the idle mixture screw should now make a difference.
The above assumes the 2100s was correctly rebuilt, and Dr. Goodpliers (the evil twin of Mr. Goodwrench) did not swap parts from a different YF.
EDIT: Just noticed this was your second post. WELCOME!
Jon.
Last edited by carbking; 09/19/2018 3:03 PM.
Good carburetion is fuelish hot airThe most expensive carburetor is the wrong one you attempt to modify. If you truly believe "one size fits all," try walking a mile in your spouse's shoes!The Carburetor Shop | | | | | Joined: Sep 2018 Posts: 17 New Guy | | New Guy Joined: Sep 2018 Posts: 17 | Thanks, I plugged off the vacuum line going to the brake system. Set the mixture screw to 1 1/4 turns out. With the gasket I made with the cutout for the hole under the mixture screw. It runs super rich. With the said hole plugged, it runs way better,but the thottle setting screw has to be screwed almost all the way in. Sounds like I will have to do more research. So much for a quick fix 😀. May have to send it to an expert.
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