Notey1

Thanks Blue, I haven't check the manifold yet, so I will do that!

I did some more checking, still no joy. Choke cables are frayed and need to be replaced, but that isn't the problem. Pistons move freely, nozzles were in position. I tried messing with the slow speed screws, but could not get the idle to drop. The service screw is not making contact, so that's not the issue. I'll check out the cable at the linkage bar,and play with it some more this weekend and see what happens! Thanks for the help!

Thanks for the comments Bruce! I'll double check the choke cable, the pistons and the nozzles tonight and let you know what I find!

Yes, the return springs are present and in good shape. Manually moving the linkage doesn't have an effect on the idle speed. Could the needles be hanging up and causing this issue?

I'm new to this forum, and looking for some help. I have a '69 roadster 2000 with SU carbs (rebuilt about 7 years ago). They were working fine until the other day. When I first start the car, the idle is fine, around 800 rpm. After driving for several miles, the idle moves up to 2000 rpm. After driving further, it is up to 3000 rpm. It is not a linkage problem, and I cannot lower it by manually operating the throttle. Everything looks clean, and I haven't found a vacuum leak. Dash pot oil looks OK. The next time I drive the car, the process repeats. Any ideas?