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Old 04-21-2006, 02:30 AM   #1
Sycamore OP
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Joined: Mar 2006
Location: Dubai, United Arab Emirates
Oddometer: 1,697
KTM 640 SM Exhaust modification


I need a few words on modifying a stock 2002 KTM 640 SM (yes, SM) muffler (shown pic 1 on attachment).
I just want to open it up a little. I have tools, 2 hands, half a brain and not much money.
I hear the groans already (not ANOTHER exhaust thread), so let me explain: I've done as much reading as I can on this forum (including the LC4 stickies), and either they are talking about some other exhaust, or there's a step that I'm missing, or some terminoilogy I don't understand. Call me dumb, that's*ok, but just help me out here.

When I pull off the end cap at the back of the muffler, I'm faced with a solid steel plate about 2 inches down into the muffler. It has a spherical bulge in the middle, gaps around the edges, and is held in place by 3 welds at the outer edges. Almost flush against the edges of the muffler is some steel mesh. (Pic 2 on attachment).

What is this plate and what do I do with it? Is it a spark-arrestor? If so, should it be removed? Cut or grind through the 3 mounting points or welds? Would drilling holes in it do anything?
Knowing this would at leat get me started, any further info would be welcome.

TO AVOID BOGGING DOWN THE FORUM WITH ANOTHER ZORST THREAD, anyone who has done this procedure is welcome to email me at so I can ask questions direct. I'll be very brief and wont spam you, promise.

Thanks all.
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