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Old 03-09-2013, 08:11 PM   #2
Blue&Yellow
but orange inside...
 
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Joined: Jan 2010
Location: Sweden
Oddometer: 754
Quote:
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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