They have rather small ports and are not the most powerful gas engine around. The hub and back plate required is the same one used with the Homelite. I converted a 21 cc trimmer. I put a much larger Homelite 25 stock caarb on it and still, it was nowhere near as powerful as the Homey 25. You want to shoot for around 7,000 rpm. Try a 14-8 and see what you get. It's been a while with mine and I sold it some time ago.

Enjoy,

Jim