Slow runniing problems Stromberg carbs.

[rgh0]

When you blank off the rear carb you get twice the flow through the front carb feeding the rear cylinders through the balance pipe. You probably end up with a better and more stable mixture to all cylinders in this situation.

Have you had a look at the pistons in the carbs and see if they are stable at idle speed. If they are unstable and moving up and down this will produce the rough idle. Cause of unstable carb pistons can be things like worn dampers or wrong oil in the dmapers, or valve leakage or other leaks giving unstable manifold vacuum. The springs that act on the pistons also may need replacing if they have lost their tension

reards
Rohan

[saildrive2001]

Good point Rohan, I will try to run it again today & check the pistons but I don't think they are moving up & down. I might have a problem even getting it to idle long enough to be able to see what happens.