Haflinger Engine Idle - Carb

[Garrycol]

Posted this over on the TheHaflinger Forum but thought I would also post here to pick up the Pinz and Mog expertise on the Zenith NDIX Carb.

I am doing a tune on my engine and need to set the idle mixtures. I have the engine warmed and the idle mixture screws wound out half a turn and idle upped to about 900RPM so that I can adjust the idle mixture screws to get max revs.

However I cannot get a stable idle - in approx a 25secs cycle the revs increase dorm about 900rpm up to about 2400rpm and then back down to around 900 RPM then back up and down again - over and over. The accelerator cable is not attached and the carb is doing this all by itself. See this youtube vid - you get the idea in the first 50 secs or so. https://www.youtube.com/watch?v=fDgyuyURAVk

John over on TheHaflinger Forum suggested that air may be getting in so I completely dismantled the carb and cleaned everything with carb cleaner and compressed air - nothing abnormal found - all gaskets are good, butterefly spindles are good, no dirt or corrosion so there is no obvious place for air to get in.

So I am looking to ideas from people with NDIX experience on what might be going on here.

Thanks

Garry

[Tjerk]

And the governor linkage?
Tjerk

[Garrycol]

I do not have a governor on this engine - completely removed.