Carb Problem

The secondary throttle plates are likley hanging open a snudge.

First adjust the pivot on the throttle cable so that at idle, the cable gently pushes the throttle against the idle stop.

Then, adjust the closing linkage to the secondary throttle shaft so that it forces the secondaries fully closed, and doesn't permit it hang open. You will need to adjust the bend in the rod with two pliers.

If you can rotate the secondary shaft with your fingers when at idle, you can hear the rpms change, and it needs adjustment to prevent your symtoms.

Another, less likely cause could be the mechanical advance getting stuck and not retarding till you shut down, pop the cap off and check for smooth operation and no broken springs; if it flops around and does not spring back, a sping is broken; if its sticky, well, it needs lube.

GottaSki wrote: The secondary throttle plates are likley hanging open a snudge. First adjust the pivot on the throttle cable so that at idle, the cable gently pushes the throttle against the idle stop. Then, adjust the closing linkage to the secondary throttle shaft so that it forces the secondaries fully closed, and doesn't permit it hang open. You will need to adjust the bend in the rod with two pliers. If you can rotate the secondary shaft with your fingers when at idle, you can hear the rpms change, and it needs adjustment to prevent your symtoms. Another, less likely cause could be the mechanical advance getting stuck and not retarding till you shut down, pop the cap off and check for smooth operation and no broken springs; if it flops around and does not spring back, a sping is broken; if its sticky, well, it needs lube.

I removed the throttle cable when this was happening but it did not make any difference. Therefore, I am thinking that the problem must be tied to the operation of the secondary throttle shaft.