New muffler was $8

[grhanka]

I replaced the massive straight-pipe muffler on my son's 125cc with an 8HP lawnmower muffler. It sounds good, nice and deep and still loud, but not as loud as it was. Also shaved off a couple of pounds. I think the stock muffler was oversized and overloud to appeal to young boys.

Oddly, I had to upsize the idle jet. This violates what I thought I knew about backpressure. The bike seems at least as powerful as before.
The new muffler is $8 on amazon. I tried a different model lawnmower muffler (see the pic) but it sounded awful.

https://www.amazon.com/gp/product/B002EP9RS0