Last week the bottom right arm just locked up to the point of requiring a retraction force that I was uncomfortable with. So I thought, here’s a chance for a service, and also time to fix those encoders.
This is what I found with the idler gear
It simply wouldn’t turn. With some spray on engine degreaser, it was really easy to clean this crud up both from the bar and the inside of the idler gear itself, and then it would spin easily. However, I found that three of the other arms were exactly the same. So, all were cleaned and re-greased with the silicon.
From the perspective of the next iteration of the M4 I’d say that adding bearings for the idler gear should be high up the list.
Anyone else found their idler gears immovable by hand whenever they did a service on the arms?