I'm just a noob myself, but this sounds like a bad idea to me. What a motorized bicycle needs is not high RPM like an aircraft motor, but torque, and plenty of it. My little Grubee 66cc goes nice and quick on level ground AND up steep hills. I go up a real gutbuster on my way to work - even my 48V Aowa e-bike struggles up it, but today the little Grubee took it no problem at 20MPH, and I was only at about 1/2 to 3/4 throttle. I was amazed at how much power that little motor packs. I barely have to give it any gas at all to go the legal limit for MB's here which is 20.
Shh... I had it up to 33 or so yesterday afternoon on a canal path before I got nervous and backed off - it still wanted to go faster. Wheeeee!
Also, none of these gas bikes are just "get on and ride". There's all sorts of fiddling and adjusting with these as they break in, and you have to keep them maintained well too - check your chain, spokes, etc before each ride. Once a week, you have to check your brake pads, they wear out quick, check your tire pressure, check the spark plug, all that. If "get on and ride" is what you're after, the Aowa e-bike I have is good for that. Just charge it up and go. They make a 36V model that's around $300-400 or so, the 48V one I've got (I know I said 36V in an earlier post but I've since looked at it again. It's the 48) is $500 or so. Just charge it and go (but don't get a flat - it uses 22" tubes which are a PITA to find).
Good luck, and welcome!