Does your bike have a drivetrain like the one in this picture? Nice bike!
If so, then the engine is Honda GXH50-style, and the transmission is the Grubee Stage III. Doing a search on either one will show you more info.
The engine is easy to get back into good running order, as it really only requires a clean carb, a plug and oil change, and a valve adjustment. The factory carb on those engines is a bit finicky, has to be just about surgically clean for it to work properly.
The transmission, on the other hand, is a charlie foxtrot waiting to happen, IMHO. Those old gear-drives were neat when they came out, very compact, but require a steady diet of good grease, preferably lithium. Some have tried sealing the case and running them with GL-5 gear oil. They've been known to randomly blow up, I have a busted one in my toolbox from back in the day. All you can do with it is lube and pray.
Other than that, the rest of it is making sure brakes and chains are adjusted and tires are aired up!
Thanks for the info, I updated my post. The same applies - these are the keyed shaft engines - so if the clutch needs to be replaced, or the transmission needs to be upgraded to belt drive, these take different parts.