Thought I would pass this on to those contemplating Zenith 40TIN rebuilds,throttle cams are a wear part and are extremely hard to find,in fact I've only seen 1 nos set in many years I have been researching.
AA had a set on ebay for a reasonable price but wanted crazy money to ship them to my US freight forward,I asked them about the shipping and never got an answer,I paid 25USD for these in a $12 combined shipping deal with a heap of parts for my 36 Dellorto's.
It appears this ebay seller has basically all rebuild/wear items for the Zeniths now,I have asked them in the past for parts not on ebay and they have come through.Click to view attachment.

My old ones had "flat spotted" @ the highest point of the cams,this causes more friction on the guide rollers which wear at a similar rate,the fix for the guide rollers is to turn them around on the axles so you have a new surface to run on.
The other benefits replacing these is more equalized throttle action and any wear on the throttle arm pivots is gone....adds a bit of bling also