Re: Is there a go-to thread for what you'll need for a build?
All i build are two strokes but I have extensive experience with karts and minibikes so I can tell you quieting a four stroke is easy. Just add whatever muffler you like to the stock pipe.
I usually went with the tube style briggs mufflers from older lawn mowers because it is small and easy to mount.
If more is better, then too much is just enough.
If you can't afford it, build it yourself.