Check that the bearing for the lateral arm (arrowed)
moves freely by rotating it by hand. Also that the linkages that operate the trip pawl are also free from grease.
Its now time to refit the cam to the sub plate.
Ensure the pickup operating lever arrowed
is moved to the right, it will be moved back when the cam is refitted.
Ensure that the brass insert is fitted.
With your finger move the lever to the right.
Now fit the cam onto its spigot, release the lever and rotate the cam in both directions till it drops fully into place. the brass bit arrowed fits into the hole in the cam.
On the cam
you will see its circlip and a spacer, the spacer must be fitted below the circlip
Move the pickup operating lever from the pick up arm (pic 1 this post) back onto the cam