Get your compression back with new rings, PW50 rings fit perfect.
It's the same engine as Benelli G2, look to see what's been done to that before.
On the cheap use a pocket bike pipe, for a bit more $ I'd go with a Proma GP or Boss.
I'm pretty sure you can also use the header from a Minerelli or Morini for an easier swap, the one on the stock exhaust is very short and stubby.
It also has a 14/12 carb so you can up grade that, and if memory serves me (unlikely) the intake was 12mm with at least 3mm to spare so that can be bored out as well.