Q about drilling out stock muffler

I know this has been covered quite a bit, but after using the search function extensively I still was a bit confused on something. My bike came used with an HRC tip, so I had never modded the stocker before. So, I was using a 2" hole saw on my friend's bike (which will forever be named the "Big Red Dog" after my dogfood post), and cut through the restrictor at the end of the muffler. Everything looked good, but when I shined a flashlight down the exhaust, there was a plate about 1/4 of the way down the muffler that wasn't there on the HRC tip (at least I think it isn't.

So, my question. Should I keep using the hole-saw and take out the plate 1/4 into the muffler? Also, will that defeat the spark arrestor by sawing out the plate (according to xr650r.us the SA is not bypassed by cutting the restrictor out, but nothing about this plate?). Also, I wanted to make it under 96db (which this muffler supposidly can do with the restrictor cut out), but will removing this plate raise the muffler noise above that? And lastly, is there anything else that can be done within the above constraints? Thanks everyone. My friend was about to just go ahead and drill it, but I thought I'd ask the experts first.

PS - Anyone know if the HRC tip is a S/A?


I had the same question. First I drilled mine but then later on I wanted the HRC tip so I bought one. When I pulled the drilled tip out I thought they looked identical except the drilled stock one is just shorter. So I think if you do cut that plate it will probably do away with the sparkarrester. Pull out your HRC tip and compare them and you will see. This is only my gues as I don't know exactly. But I would wait until someone who does know can give you better info.

Good Luck

No, DO NOT drill that plate. If you do it will defeat the spark arrestor.

Thanks much. Just the answer I was looking for.

On the back of the spark arester is a four prong baffle that you should remove but, don't remove plate at the back of the screen. It works great to bend down or remove the two plates that are in the muffler housing that the tip slide through. :)

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