I am looking to modify the stock mufflers on my bike. All I am really looking for is a little extra noise (don't need enough to blow out windows). Specifically, I was wondering if drilling a hole/ holes in the baffle endcaps (facing upstream towards engine) would have the desired effect. Anybody have any idea how much I could open it up without significantly affecting performance and if this would be enough to get extra sound? Also, when you reduce the backpressure, does this make the bike run rich or lean?

Thanks

 

To sum it up in a few words...."don't do it"

It sounds terrible and runs poorly. It will run lean IF you do it and you will also loose bottom end torque, but if you like whistling, farting, tinny, cheap sound, then go ahead and do it. Get a set of cycle shack or SEII slip ons and be done with it, you may need those stock mufflers when the EPA police come looking for you too.

 

If you want to try it, buy a set of cheap stock muffs on ebay for your bike. Do the mod on your mufflers, and if you are not happy with the results, install the ebay mufflers. I punched a friends pipes for him. He was happy with the sound, but still has his ebay pipes in case he wants to go back.
Personally, I wouldn't waste my time or money. I bought SEII slip-ons, but now wish I had gone with the Cycle Shacks. They are basically the same thing, but alot cheaper!