Thanks for the replies. I've never noticed Part #3. I ordered these 4 items that make up part #3 because I needed the other part. I don't know that the part #3 tubular item is worn or not, but after 36 years you'd figure it wouldn't hurt to replace it. Do you know which way it is removed? Bowl side (bottom) or throttle side (top)? Here's a better picture of part #3. It appears there's a gasket between part #17 (main jet) and part #3 tubular piece.
I also order a Keyster carb kit on ebay, their description said that the #60 main jet is the correct jet for the '74 and '75 Z50. HONDA Z50 Z50R KEYSTER CARB KIT 1974 1975 - eBay (item 220694624839 end time Dec-09-10 08:09:31 PST) According to the microfiche the '74 carb uses a #55 main jet. Does it matter a whole lot which one you use on this stock carb? :?
I also order a Keyster carb kit on ebay, their description said that the #60 main jet is the correct jet for the '74 and '75 Z50. HONDA Z50 Z50R KEYSTER CARB KIT 1974 1975 - eBay (item 220694624839 end time Dec-09-10 08:09:31 PST) According to the microfiche the '74 carb uses a #55 main jet. Does it matter a whole lot which one you use on this stock carb? :?