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Old 03-09-2013, 08:11 PM   #2
but orange inside...
Blue&Yellow's Avatar
Joined: Jan 2010
Location: Sweden
Oddometer: 754
Originally Posted by Yam2Yam2 View Post
Hey, guys and gals.

As have many of you, I've been modifying mufflers for more power, and in three cases, modifying for less noise. I think I've hit on the easiest mod, while still keeping power output high.

Many years ago, I gutted a tall spraycan, and built my own add-on can, with fiberglass packing, and a screen-door wire mesh inner pipe. Now-clearly we don't want to do that on our WRr's, but I found that placing curves in the inner wire mesh (IE not a straight tube) massively reduced the bark of that two-stroke.

That led to tonight's very quick test. I had 1/4" wire mesh on hand. I cut a length of 4 feet by 4 inches. I then tapered 3 of those feet from 1 inch wide to 4 inches wide. When rolled into a two-inch roll, this gave me a cone-shaped interior. It has a shape similar to looking into the spark arrestor.

When placed inside my brand-new and very loud PC4 muffler, so that the cone is widest toward the engine, the nasty sharp-edged bark at WOT is reduced very greatly. There's still a nice low rumble, which I believe means I've still got good flow. (It's raining snow, so I won't be riding for a while yet...)

I'll be making a slightly longer version tomorrow, and plan to take picks and a before and after video. I'll use my Radio Shack DB meter, too.

I hope that this mod will give me appropriately quiet street operation, and still give me the power boost that I want.
I'm always interested in stuff like this but I think your post needs some pictures or sketches - not easy to picture what you're saying.
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