spark arrestors

A spark arrestor must be stamped with a USFS approval code in order to be legal for use on public land where S/A's are required. Typically during a tech inspection at an event, a metal rod will be inserted into the silencer. It can enter no more than 20 inches. I've seen people that have modified non-S/A silencers using screens and other items to pass a tech inspection. However, it is not a "legally approved" S/A and they can still receive a ticket.

I read that article, too. It said that even if the unit was stamped USFS approved, it may not be. It has to be listed in some book that the USFS keeps of all approved SA's. However, I don't think the article told you how to check to see if you're SA is on the list.

Are you sure you need 84db? That's very quiet. I don't know if anyone makes one that quiet. I think MN is 95db to be legal.

You'd have to check with the manufacturer of the silencer to see what they say about the sound level in your application. Glad to see you're trying to get legal. Many bikes are just too loud.

Spark Arrestor List Needed

Does anybody know of any available list of approved spark arrestors and/or muffler noise levels? If not, maybe we can get create one here(?)

According to Jeff Applegate, with the US Forest Service, (Mendocino Forest/Stonyford. The USFS approved stamp is the "legal" one, however, this does not mean that it meets the sound requirement. California 99 dba plus 2 dba, 101db. Idaho is 96 dba. US Forestery approved is NOT LEGAL. Jeff indicated that they are working on stamping approved on spark arrestors which also meet the sound requirement. They are aware of many USFS approved spark arrestors which do not meet the sound requirement. Enforcement in California will begin soon, rider education, friendly sound checks without the ticket book are still going on in CA. It is the riders responsibilty to make sure ones bike is quite.

The current issue of Dirt Rider had a four-stroke silencer/spark arrestor shoot out and the the best was 101db, way to loud! I think Dirt Bike should tell the after market manufacturers to take there loud illegal exhaust systems back to R & D if they expect favorable ink, otherwise the article should have shown a photo of a bunch of spark arrestors and silencers being thrown in a trash bin. Design and market legal systems that produce good power and stop encouraging the purchase of these obscenely loud and illegal spark arrestors/silencers.

Dave Wood

The noise generated from a four stroke is of a lower frequency sound and therefore it is more difficult to attenuate.

i have heard alot about that stuff in the states... does anyone know if any rules like that are going to apply in Canada?