what does a spark arrestor do?

 

It keeps SPARKS from coming out of your tail pipe and catching the woods on fire. only happens really when your runing fast.

 

like how fast are we talkin?

 

I really hope that savage was joking around wiht his reply. A spark arrestor does keep sparks from exiting the tailpipe. Sparks can exit the tailpipe ANYTIME your engine is running. Without it, you can potentially start a fire if you are riding where there is vegetation. If you are riding on public lands they are most likely required by law, although it does vary around the country depending on the flammability of the vegetation ect. There are usulaly unpleasant fines associated with getting caught without one. If you do start a fire through your neglegence, (I.E. riding without one where it is required), you will likely be fined and asked to pay suppression costs- this will be a lot of money in very short period of time. All OEM atv's come with spark arrestors in the silencer, they usually consist of a fine screen or a chamber designed to let the glowing carbon fall to the bottom of the silencer while the exhaust gases flow out.