PO drilled holes in my muffler...!

[lucky23]

it looks like he drilled three holes in the rear baffle of each muffler of my R80...would that affect my carb jetting/tuning? I doubt he did anything to compensate for the holes....

[88bmwJeff]

What year bike? How big are the holes? And, can you describe or post a picture of the holes? I've heard some guru's comment on the benefits of small holes drilled in rear of the mufflers. I can't remember why, and I believe it applies to the dual shock models.

[lucky23]

it's a '79. The holes are about the diameter of a pencil...

[ducatipaso]

haha I did that to my old '79...

[vanzen]

Drilling holes through the baffle of a BMW muffler is an old hot-rod-boxer trick.
Although a single hole of 3/4 to 7/8" diameter was more popular – and more easily accomplished,
a number of holes resulting in the same cross sectional area would be effectively the same.
The concept is that the stock unit is power restrictive due to EPA db regs
and, although the modification increases noise (mostly noticed under acceleration),
it is also claimed to improve "mid-range power".

I've drilled quite a few cans ...
will say that the procedure is "seat-of-the-pants confirmed" ...
but have no dyno sheets / statistics to validate the results ...

[brentde3]

I just had my mufflers off for the first time last night. No holes, just rattles. Rattle-cans, get it? :whistle

[bikerfish1100]

yeah, 'twas a common mod of the late 70's. did it on my '78RS (internal baffle at the weld)- made a nicer sound, but not much power bump. no jetting change needed.

[lucky23]

Thanks...i'll just keep em then! it does give it a tad more growl....