Yes, the 460's power is geared to drive the bicycle's front chainring and its 8-speed cassette. This setup utilizes an obsolete Scooterguy frame-mount drive kit. Along with the brackets is a 5:1 pocket bike transmission. This bolts directly to the GP460 bell housing. An 11-tooth drive sprocket slips onto the transmission's spline. It then chains to a 63-tooth chainring which replaces the outer bicycle front sprocket. The inner bicycle front sprocket has 30 teeth and drives a bicycle chain to the derailleur. Gear ratio at this point is 28.64:1. First gear on the 8-speed cassette has 34 teeth, for a ratio of 32.46:1. Progressing through the gears, the ratio decreases to a final drive of 10.5:1.
There is no machining involved in my installation. However, since I'm using 4-bolt freewheels at the front bike sprocket, the bike's chainring had to be drilled to bolt onto the freewheel.
You can find everything you need from the pocketbike vendors online and from SBP (Sick Bike Parts).
My friend's NuVinci gear ratio probably ranges from 38.35 to 7.67:1.
What you are proposing for your 460 engine install is not practical. Why? Because this engine has a high-rpm power band. A single gear ratio will not be the right choice, especially when riding from flat ground to moderately steep hill. Halfhway uphill, the engine will bog down and expect you to pedal-assist to the top of the hill. The engine needs to have its revs up. There is no sprocket big enough to run on the left side without step-down gearing like a gearbox or more than one jackshaft. This engine loves to run with stiff gears, then cruise at 19:1 ratio.
One possible way to frame-mount a small engine is to fab or buy a bracket to position the engine. Your clutch would need to face the bike's cassette's side. Then bolt a 5:1 pocket bike transmission on, with an 11-tooth spline. From there, you could follow my path thru the rear cassette.
If you still wanted to utilize a left-side rear sprocket, run an 11-tooth drive sprocket to a 15-tooth jackshaft sprocket. You have 6.82:1 gear ratio at this point. On the left side of the jackshaft, install a 13-tooth sprocket, then chain it to a popular 36-tooth driven sprocket. That will give you a good start with final drive of 19.07:1.
Good luck.
