I’m using a Honda GX35 (35cc) 4 stroke. I have also used a Chinese 50cc 2 stroke from a Harbor Freight auger. I’m sure the Honda is a better engine and will out last the Chinese engine hands down, but I like the power of the 50cc engine way more than the Honda. Only about ½ horsepower difference, but that alone makes a big difference in these little, low powered engines. Polk 5-7 for more info about what he uses. He said he uses weed whacker engines, but they’re also Mitsubishis or Tanaka close to 50cc if I‘m correct. My Honda is also used on weed trimmers, but it or the Mitsubishis are not typical Chinese made engines. Check you local state laws and go with the biggest engine they allow. You’ll be glad in the long run. Honda, Mitsubishi, Tanaka and Robin/Subaru all have excellent ratings.