Welcome djat,
Just a note, there is no such thing as an 80cc, it's a 66cc for accurate future reference ;-}
Unfortunately just moving your rear sprocket out won't do it.
That 415 chain has to be in alignment.
Your engine sprocket is inside the tires width mounted to the seat post, ~2.25" tires is all it can get by.
That means either also making an offset 2-stroke engine mount for front and rear, use a different system like a friction drive, or just 'jackshafting' your engine output to the right hand side and using the pedal system to drive the wheel.
SickBikeParts has a 2-stroke JS kit that works well for $200.
http://www.sickbikeparts.com/catalo...ducts_id=86&osCsid=rg0jf2im21ou0prpq2sfsuihc2
You mount the engine to the JS base, then mount the unit to the bike, and then change out your bottom bracket pedal system that will share the pedal drive with the engine and not beats your legs off.
Read the install instructions as it's complicated and may be above your skill/tools level but what I use for everything with over 2.25" tires like this one.
No extra back wheel sprocket, the engine goes to shaft.
Then, you use the pedal side which is already wide enough to clear your fat tire on the right.
Bummer you have no rear wheel gears you could use with it as well, but it's better than trying to go the other way as you want your engine secure to the frame.