1.=C
2.=D
3.=B
4.=B

1=#3
2=#4
3=#2
4=#2

Damn,
I only got 3 out of 4 right. Had to think and study the images for abit, looking for certain characteristics.

#1.  1951 Honda Dream Type D  
Too easy

#2.  1976 Suzuki RE5 Rotary
The Water Buffalo!

#3.  1966 Honda CB450 Police Special
With that tank it could only be a Honda!

#4.  1982 Honda NS750
Based on the Honda CX500 motor

The term "Water Buffalo" was US slang for the Suzuki 750 2stroke triple watercooler...circa 1974 I think, made for three years or so.

In England they tended to call it a "kettle".

In stock form, they were actually pretty mellow, esp. for a 2stroke that size.  I knew a guy who adapted a set of Kawasaki H2 aftermarket chambered pipes to a water buffalo plus did some very basic jetting, and the dang thing turned into a screaming beast :).  He said it was the most bolt-on horsepower he'd ever seen or heard of.

Which led to a problem: the stainless-steel front brake disks were utter crap, and he had no good way of slowing the evil beast down :).

Later, this same nut did the wildest bike engine swap I've ever heard of.  He found a crashed RD500 Canadian-spec 2stroke 4 cylinder bike, pulled the engine, gave it the full treatment, dropped it into a FZR400 frame and running gear :).  He didn't *quite* succeed in building something that could keep up with a GP500 factory racer but he claimed it was damned close.  Dunno for sure, I wasn't crazy enough to swing a leg over it :) but I *did* see the critter.