Mk 2 Amal hanging up

Just finished refreshing my ‘72 750 Roadster which languished for too many years. Has less than 15K miles on a single Mk 2 Amal that I fitted in the 80s. Thoroughly cleaned the carb and installed all new jets, float, and needle. Everything works as advertised statically - cable moves smooth and freely and the slide snaps right back to the idle stop. 2 kick starter with a nice 900-1000 RPM idle. However…when revving it, it will NOT return to idle, almost wants to run away. It’s like the slide is hung up, but after shutting it off, the slide is sitting right on the idle stop. Side note: has a Tri Spark ignition.

Been through the remove/clean/install/test fire/fail scenario a couple of times - same result.

Any ideas/suggestions? Thanks -

Drop the idle stop by unscrewing, if the revs stay high you have an air leak. To find the airleak spray wd40 or similar over the manifold joints, when the spray finds the leak the revs will change.