Re: head tube replace
You could get a silencer for the 79cc to quiet down the exhaust some. Its a good engine, a couple of my buddies have used them and it's what sold me on it for my first build. I haven't run the engine, but I'm not so concerned with noise. I got a Shorty exhaust from affordable go karts. No idea how loud it will be, but the description said it provides decent flow while still maintaining a reasonable exhaust note.