1979 510 wagon; cold start wont hold RPM to keep engine running

[RAUL DELGADO]

I have a 1979 510 wagon and just recently I rebuilt the carburetor double checking the assembly of all parts and gaskets and now the cold start is not maintaining the rpms up to keep the engine running. I adjusted the cold start automatic choke at the carburetor and no changes to the problem; the idle adjust screw does no effect to the adjustments, I checked the timing and it is correct right on the dot. I check for leaks around the carburetor as well as the intake but nothing found. Frustration is getting closer to make the decision of buying a new replacement carburetor. Please help.

[datzenmike]

 When the choke is on a rich condition is forced which assures that all the oxygen is burned and keeps the engine idling. Part of the choke assy is a fast idle cam that slips into place between the warmed up idle adjustment and it's stop. As the choke warms up and opens the fast idle is free to drop down out of the way and allow the throttle to close all the way to it's warm adjustment.

 

If you hold the throttle half open and open and close the choke flap you should see the plastic fast idle cam move in and out of position.

 

Sometimes they stick open or closed, and a liberal spray of WD-40 over the linkages while moving them back and forth usually fixes the problem.

[DanielC]

There is an adjustment between the choke plate and the fast idle linkage, usually by reducing or increasing the bend in the rod going down to the throttle linkage.  This bend controls how much throttle is applied with a given choke plate closing.

The idle mixture screw is only to set the idle mixture on a hot engine.