a discussion has been taking place as a new member attempts to get his Mark 5 up and running
He has a broken control sheave loop, and a control sheave stuck in slow.
The belts appear good and he does not want to destroy them.
He has suggested that he may need to take take the floating sheave off the motor.
So my initial reply is:
No you do not want to take the floating sheave off. That is quite difficult enough with the belt already removed.
Since the control sheave seems to be 'stuck', the approach I would take, is to first remove the speed control. The knob has a small set screw that is a bit of a challenge to locate, then loosen. After removing the knob, there are three screws that secure the speed control to the headstock casting. One has a leaf spring attached(upper right). Remove those three screws and since the loop is disconnected from the porkchop, the speed control should now be removable.
The hole under the speed control is quite small on an "A" headstock, but it does give you access to the control sheave. Penetrating oil and gentle prying may allow the control sheave to move away from the idler sheave and possibly off the inside end of the idler shaft.
That will allow the floating sheave on the motor shaft to close, or provide slack for the belt so it can be taken off the motor pulley.
That will allow you to remove the motor pan/motor. The idler shaft can be removed towards the front of the headstock(goes IN). There is a screw that squeezes the casting around the idler shaft bearing, and a set screw that holds the eccentric to the bearing. With the screw loose, the eccentric can be rotated to slack the internal belt(Gilmer or Poly-v). The set screw can be accessed through the slot under the bearing.
Nuf fer now!
Goldie(Bought New SN 377425)/4" jointer/6" beltsander/12" planer/stripsander/bandsaw/powerstation /Scroll saw/Jig saw /Craftsman 10" ras/Craftsman 6" thicknessplaner/ Dayton10"tablesaw(restoredfromneighborstrashpile)/ Mark VII restoration in 'progress'/ 10E(SN E3779) restoration in progress, a 510 on the back burner and a growing pile of items to be eventually returned to useful life. - aka Red Grange