Team MightyBoy

My son has a Mighty Boy.
It's a great but the 550cc motor is blowing smoke like you would not believe it also has a four speed gear box.
Question 1
What motors can be put in the Mighty Boy?
Question 2
What the easiest motor to fit?
Question 3
What if any can you fit a 5speed gear box to?

So in summary.
We are looking for the easiest and largest motor preferably with a 5 speed box.

Time to butter up.

I’m sure that these questions are very simple to those of you in he know.

Thank you.

Sned87 wrote: I’m sure that these questions are very simple to those of you in he know.

Also very simple to find the answers with the "search" button.

But to give you the short and dirty:
#1: Suzuki F5A, F5B, F6A, F6B, K6A (all imports) F8B, F8C, G10A, or Daihatsu CB61/71 will all fit into an MB.
#2: Suzuki F8B - bolts straight in with no modifications.
#3: Any of the import Suzuki motors I mentioned above will have a 5 speed box, but obtaining and fitting these boxes is the challenge. The domestic F8B four speed has taller ratios than the stock F5A and is adequate for most people. (including me!)