It's not my car but I did make the diff setup. It is my friends 1990 Geo Metro with a Honda CBR600 bike motor

 

There has been a lot of bull shit going around why the builder chose  such a small motor.

 Of coarse we know a hayabusa (or any motor over 1L) would be  faster and cooler.

turbo'ing was also in the plan

The CBR 600 was chosen to prove the concept.... and it was damn cheap.

why spend the big bucks for a hayabusa if the diff blows up?? or any number problems the could have arise.

This is a prototype, if you don't like it fuck off.

 
I did not build the car, so I'll do the best I can to write the captions
  It uses the stock Metro radiator
  and it uses the stock motorcycle battery 
   
  I know that the builder had a hard time with the fuel system.. I'm still not sure how it works. It use the Metro gas tank and fuel pump then is regulated down to a very low pressure that's  sent to the bike carb's
   
  I've been told it's reallllllyyyy loud on the inside. All extra weight has been removed
  Light weight plastic racing seats
  Motorcycle gauge cluster, the speedometer currently does not work
  Sequential shifter..... It is the Geo's automatic shifter modified
   
  A good look at the shifter linkage and the diff that I did. The diff is the stock Geo's diff and half shafts with a sprocket bolted on were the ring gears goes
   
   
   
  The car is so light it does not compress the suspension any noticeable amount, So the springs were cut in half.
  Reverse??? that's why there's a  passenger seat (Fred Filstone style). Notice the cool aluminum diamond plate chain guard.
  Here's a pic of the work I did.

Its a stock metro diff. I machined a blank sprocket to bolt were the stock ring gear used to be. Then we found a sealed version of the ball bearings on the diff. Next I CNC'd the bearing cassette. The bearing presses on to the diff then gets pressed into the cassette.

 
  Then I bent up some 3/16 plate for the cassette holder
  What about oil? a little WD40 every now and then seems to be working. Maybe use some grease later. But what is the worst that can happen???  spider gears seize??? turning it into a spool, then we will weld it up permanently turning into a spool.

Later on we will find a sealed viscous diff., solving  any oiling issues

  Bolt heads had to be modified to fit around the bearing cassette.

 
   3 more super bike powered geo metros to come?????