Topic: is this part necessary?

[Dysil]

rebuilding a 75 cb550 and wondering if the plate/guard that goes on the outside of the rear sprocket (part#2 in the photo) is necessary. what does it do? is it necessary for spacing in the swingarm? can it be removed?
just curious

[TwoTired]

It's for rider safety  (who needs that, right?) 

Should rock wedge under the chain and throw it off the sprocket, that guard keeps the chain from wedging between swing arm and wheel, locking up the rear wheel into position at speed.  Some riders might not be able to handle such an event without crashing and injury.

So, it depends on just how invincible you are, I suppose. 

Cheers,