Rusty the hub has to be flat, no taper, for the hub adaptor to work. The best and most common hub size is 1.5" diameter as it has more surface area to "grip" the 1" hub size adapter is very prone to slip and this damages spokes. 26" wheels with 36 spokes is ideal, more spokes won't work. 24" wheels with 36 spokes is tight but will work. Larger diameter wheels will work but often have oddball hubs. Cruiser style wheels are what most use in 26" 1.5" hub & 36 spokes.
Tires wider than 2.2" can cause problems with chain rub on tire sidewall, but I have carefully fitted up to 2.5" tires that barely clear. This is a problem mainly when using the China kit engines.
Frame triangle space is an issue, motor has to fit and some triangle frames are just too small to fit the commonly used gas motors. If there's sufficient space in the triangle you can motorize it with a gas engine. If not find another frame or use electric motor to power the bike.
Obviously many frames work look at photos in the forum to find frames that suit you. This hobby is a learning process, but thankfully there's lots of examples of what has worked to get you started. Unfortunately there's a great deal of mis-information out there so always take any free advice with a grain of salt, mine included. Think it through and always measure twice before proceeding.
Rick C.
