Here's the scenario - My buddy has a 1977 or 78 Express that I am welcome to. The engine will not start or even turn over. "Experts" told him it's beyond repair. Here is my question: Will this 1981 Honda Express motor & tranny (see attached picture) fit on my friend's 1977 or 78 Express? The motor/tranny is a little pricey, but if I could get it and install it myself, I would have a fully working moped for a fraction of what they're selling for complete. THANK YOU SO MUCH FOR YOUR HELP. Again, will an 81 Express motor fit on a 77 or 78 Express frame?