Need help with getting new engine for my bike

[jesse]

So i got a gas engine bike awhile back and put it together and it kinda just sat in my garage for awhile cause i couldnt figure out what was wrong with the engine, and now i need to have a way of transportation so i decided i just wanna buy a new engine and retry, my problem is the bike i got has a customized piece cause of the frame and was wondering what engine i can get that would fit or if id be able to get it modified to fit?
here is the link to the bike i have: https://bicyclemotorworks.com/?s=gibson
and here is the link to the engine i would LIKE to buy: https://bicyclemotorworks.com/product/advacned-race-ready-66cc-bike-engine/

 

[Topper Harley ' Scotland]

Bicyclemotorworks really cant write a sentence! Its almost chinglish! Looks like a sweet frame though! I build from classic Raleigh and Sun frames. Im sure someone will be along soon to offer sound advice. Whats wrong with you're original engine