It is my understanding that ALL street bike stock mufflers ARE spark arrestor equipped. It is only offroad vehicles that may or may not come stock with a spark arrestor. And only offroad (meaning not meant to be licensed for street use) will have the muffler stamped that it is a spark arrestor.
A spark arrestor may be an indirect flow type or a fine screen type.
The indirect flow (Krizman patent) just means any burning material cannot go straight out the pipe. Instead of a straight-through design muffler there are a variety of ways to make it low (to none) restriction by offsetting a tube inside. That is how the Suzuki GSXR mufflers work. There are no baffles and just a very thin layer of sound deadener on the inside of the can itself, and two tubes that overlap each other which means any burning particles will hit the inside of the end cap while the gas swirls around and goes out the outlet tube. The muffler itself is light because there is next to nothing inside it! Just a very good use of sound wave modification.
The old standby test performed by Rangers and others with ticket books, was to see if they could insert a stick or similar long thin object into the muffler and have it go in past the muffler showing it was "straight-through" and therefore NOT a spark arrestor type. I don't know if they still test in this way or not. They may only look for it stamped on the muffler itself now.
Anyone else have more info on this?
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