I found an old Iron Horse engine and it seems to be in really good condition.Unfortunately, I have no information about this brand... It's a one cylinder engine and it goes on a gardenning tool.It's two stroke with vertical shaft and it's very small (would be surprise if it develops 3 hp). I want to make a motorized bike with it but I don't even know of powerful it is... If somebody know or already had experience with this kind of engine please write it! Thanks and sorry for faults (learning english... )

You might try looking here. I see a link to antique engine club on this site and it explains a little about what you have.

Ref:

Johnson Iron Horse - Page 1

Thanks a lot!