I'm looking at this kit too. There seems to be a few discussions in the archives about this motor. One earlier adopter find metal shavings and poor workmanship, other owners seem to like it and have not had any issues. Some users suggest taking it apart and inspecting the engine as a good measure for any purchase.
I wonder if it is possible to get more than 4.5 HP out of it or if it can even get the 4.5 HP that they claim it to have.
Anyway, I hope that you can find the information that you need.