I took a closer look at the knurled collar. It appears to be riveted from the inside of the collar to the chrome shaft. Does the shaft turn with the collar? To loosen the throttle is the collar turned to the left or in other words the top to the outside? Does anyone have a picture of a 1977 vintage collective on a 280C showing what the throttle friction collar is suppose to look like? This may have been altered some time. I just got around to reading all the logs on this ship, I know --dumb-- before buying, but I trusted the owner and mechanic. In 6,900 hours there has been lots of things replaced, upgraded, or added to her.