I saw on a web site that Big Gun recommends their mufflers be repacked every 20 hours. Has anyone heard of this or is this just someone wanting to sell expensive repack kits?

http://www.motojoe.com/atv/biggun/pipes/4stroke.htm

Scroll down to "Big Gun Muffler Repack Kit".

Do all mufflers require periodic repack? And if so, how often should this be done? Every 20 hours seems pretty high maintenance to me. Does the Muzzy require repacking like this?

 

20 hours is for racing applications.

In street use, I find big guns need to be repacked maybe once or twice a year (assuming 8K miles a year which is what I average on my dual sports). It's no big deal if you don't do it, the muffler just gets louder. But you should go ahead and do it because it's so easy.

The way you tell, besides noise increase, is to pop off the end cap and look at the packing. It usually burns from the end forward so if you can't see any back there, it's getting time to re-pack.