professional opinion about Baffles

[squid]

Alright. So I admit I am new to this, but I'm no idiot.
I just purchased an 81 xs650sh and I've been in the process of cleaning it up, tuning, and other minor customizations. Last night I read on this forum about punching through the baffles in the stock exhaust. Seemed easy enough to do and so today, after school, I decided to give it a try. Well, much to my dismay I realized 2 things. #1 The baffles already had holes in them that seemed to have been punched with a rod and #2 there were four holes drilled in the rear of the exhaust around the main exit hole.
Slightly dismayed because I was expecting to make my exhaust louder/deeper than it already was, I decided to punch the baffles a little bigger. I ran into no snags doing that.

I started the engine, and I began to wonder what it would sound with the 4 small drilled holes plugged. By simply plugging the four holes with my fingers, I realized that the sound got much deeper. It seems to me that with these 4 small holes unplugged there is more of an air *fwop fwop* noise, rather than a low rumble. This seems to make sense after examining the diagrams of this exhaust. With these four holes, there is less of a chamber for the exhaust to resonate, thus eliminating the lows.

I was wondering about some of your professional opinions about this theory, and if there is a simple/cheap/easy way to plug these holes that will still be aesthetically appealing. I attached a picture (hopefully) that shows the 4 holes I'm talking about. There are identical holes in both mufflers.

Thanks!

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Squid

[xsleo]

If I was gonna do some thing i would cut a washer out of a piece os sheet metal to fit just inside the chrom part with the center hole just a bit bigger than the center hole and screw it in place with some stainless screws.
Or weld the holes in and grind them smooth, a coat of high temp paint and call it good.

[coneeng]

Without opening up the muffler to be sure what the holes are actually for, I would guess they are to allow the escape of excessive pressure when the muffler reaches max capacity. Kind of like a spillway in a dam.

[Motorbikeman]

Stainless steel pop rivets will do that Quick and easy ?

[tomterrific]

The 4 holes drilled into the back of the stock muffler are a dumb guy's way of getting an aftermarket muffler. I've seen this for years, never was a fan. What the holes do is subvert the design of the muffler. As you already noted, the sound is loud and higher pitched than you (or I ) would like to hear. With the opening of the center tube (knocking off the tube's end cap inside teh muffler) the sound is slightly louder, much deeper toned, and the exhaust is freer flowing than stock.

A good welder can fill those holes with weld bead. You then can grind the weld flat and paint over the back to keep the muffler from rusting. Don't expect the welded holes to look like the oringinal sheet before the holes.

A crazy idea is to weld shallow nuts over the holes and use bolts to block the holes. You can always remove the bolts to make the bike louder.

Tom