The pocket bike "Cag" motor has been used with great success on motorized bicycles. Do a search on this forum, and you will see the results.
Various chains can be used on bike engine drive systems. You just need to find the type of sprockets. You also need to calculate correct gear ratio for your type of riding and engine drive. Most chain drive systems shoot for 18.75:1 for all around riding. I use a center-frame mount engine, which is Tanaka, not pocket bike. Using a shift kit and 8-speed rear cassette, my first gear is 46.32:1 and highway gear is 15:1. A Cag engine would do well with this setup, I think.
Pocket bike engine, chains, sprockets, freewheels are readily available @ inexpensive prices. One vendor uses small #25 chain. I use the pocket bike 8mm T8F chain and sprockets. They are very strong, and I've never had any durability issues with pocket bike chain and sprockets.
The best part is that the Cag pocket bike engine has a 76mm clutch and 4-bolt motor mounting pattern. This engine bolts directly onto all of the popular engine drive systems.
Good luck, and welcome to the club.