Chain Guard
 

Have had my 'hawk for a little over two years and it has never had a chain guard. Pretty stupid to be asking now, but how critical is it that the bike have one? Never had one on any dirt bike I've owned either.

It mostly keeps flung oil off your plastics and loose clothing out of your chain. Otherwise not really critical.

^+1 I don't use one, but if you remove it you may want to keep it, at least around here you can't run your bike on the track without one...

In Australia it is required by law as a safety item. It is to prevent any body part getting caught in the chain. All registered bikes must have one.

Depending on what state you are in it may be required to pass inspection. I know in NH it is required.