We bought our teenage son an engine kit from site supporter bikemotorkit.com for Christmas.He is not a very big guy at about 4'10" tall.He wants to put the kit on a mountain bike.I would appreciate advice on the easiest bike to motorize for him.I am able to provide any tools or skilled help he needs.He wants to do this build for himself.I'm hoping to buy him a bike that the kit is a bolt in with no or very little mods.A 24" bike would be best if possible.I would like to order him the bike from amazon,etc. because he is financing the rest of the project.We bought him the kit to get him started.His only income is working part time where he practices taekwondo so he has a limited income.Thanks all and have a great New Year.