Cs4i or yong heng

Yes I’m with you. I have had two YH’s. One needs top end rebuild, other one just hadn’t used it but once. I also have a CS4, Omega Aircharger, and a Daystate Super Leggero. Those GX compressors are pretty dependable and quiet. I love my Super Leggero and Aircharger, but mostly use the CS4. Small but powerful And easy to travel with.
If the parts were more reasonably priced I'd have less of a beef w the need to occasionally rebuild. But the sum of parts needed will put it into new YH territory.

You might as well keep any old, F-d up acquired for cannibalization. It's cheaper in the long run than purchasing new parts.