Well it raced as a 500 in this bike.
The motor originally powered a TZ750 road racer.
The bike was involved in a fatal crash at Bathurst and to my shame I can't remember the riders name.
It was owned by one of the big Yamaha dealers so they bought a new replacement factory motor because the crankcases where damaged beyond repair.
Garry my mate bought the remains of the motor and fixed the cases as best he could.
So it ran two TZ750 cylinders with open ports @ 175cc each on the left side and one cylinder from a TZ250 with reed block ports @ 125cc on right side.
So effectively the motor was converted from a four cylinder to a three cylinder.
The port configuration may have been the other way around. My memory isn't what it used to be.
It sounded like a bag full of cats fighting but it went like stink.