Technical > Wiring & Sensors

S13 and RB25 CAS Disk replacement

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rob@vems.co.uk:
Starting from the top of the CAS

Remove the rubber bung.  If you have a aluminium bung it will need to be drilled out.

Unscrew the plug coverplate.

Flip the CAS unit over and you will see the screws that hold the units peices together, some units have normal cross-head screws, this one had security screws that allow tightening only.  To remove these screws you'll need a pin punch to tap the screws anti-clockwise and free them up.  The screws will loosen and you'll find that the marks made on the screw head allow a flat blade to grip so that you can unscrew normally.

Open the vice and suspend the CAS on its locating lugs and tap the shaft out. ***Be careful not to let the top half of the CAS drop out and hit the floor - once the shaft starts to move put your hand out to catch it.

Using a flat blade crack off the screws, you can completely remove the screws and the base plate becomes free. *** The screws are very soft and will tear up easily - use a lot of down pressure and apply quick twisting force.

Suspend the top of the CAS in a vice and use a drift on the top of the shaft to knock the shaft free from the bearing. ***Gently does it, and be prepared to catch the falling assembly!

Now the component parts are free.  ***All the way through the disassemby and reassembly process watch that the 0.1mm thick disk does not get bent.

Clamp the top of the shaft in a vice and use mole grips to turn the screws anti-clockwise. Once the screws are cracked off you can hold the shaft in your hands and use pliers to speed up the operation.

Once the screws are out you can slide the shaft out of its retaining flange.

And then you have the disk in a removable state - put the locator pin at the top and use it as the pivot to turn the disk out from between the sensor slot.

Reverse the operation to put the new disk in place - the screw holes are offset in such a way that the locating pin and the screw holes mean that the disk can only fit together with the correct side of the disk at the top.

Drop the screws in through their holes in the base plate, and slot the shaft into the retaining flange, locate the shaft in the top part of the unit's bearing.  ***Now here's the tricky part... You need to tap the top of the shaft to push it into the bearing, you also need to tighten the screws to locate the base plate.  If you tap the shaft down too much you'll bend the disk against the tops of the screws.  Screw down too much and you'll bend the disk against the top of the sensor slot.  So tap a few times, then tighten the screws, repeat until the shaft is home and the baseplate screwed down.

When correctly fitted the disk will sit cleanly between the sensors in the slot.


The bottom of the CAS can be pushed onto the bottom bearing.

After screwing the two halves of the unit together with the security screws, pop the sensor plate on and fasten the screws.

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