quietest muffler

[KennyMc]

The quiet insert is simply a metal sleeve the fits in the end, the spark arrestor is always in.

So the quiet insert has a built in spark arrestor?

[rdefonce]

I took the same system off my 02 WR for the same reason and put the stock unit back on. Without an insert it's a little loud but not too bad. The stock insert was too restrictive so I bought this one and it's right were I like it.

http://www.promotobillet.com/catalog/product_info.php/products_id/54

I also have a '99 YZ400 (with stock exhaust system.) I ride in Colorado with it, and want quieter setup but that will still work on MX track. Would the promotobillet thing be a good choice for that?

[byggd]

I also have a '99 YZ400 (with stock exhaust system.) I ride in Colorado with it, and want quieter setup but that will still work on MX track. Would the promotobillet thing be a good choice for that?

Every bike is different but IMO yes. On my bike it brought it down to 92db.