What is its purpose?

Does it hurt anything having the bolt out while riding?

 

the arrestor comes off the back of your muffler if you have one. you may be talking about a plug you can take out to remove carbon from the muffler.

 

Maybe I should rephrase the question...... does it or could it damage anything while riding, with the spark arrestor plug out?

 

It should let the motor run a little better without the backpressure, letting the engine breath a little better. But on the down side, you run the risk of starting a forest fire in the fall or any very dry season if sparks comming from the muffler should hit dry leaves or something on the ground.