The RZ-500 was a consumer version of the Yamaha 500 GP bikes. Same basic engine. From what I have read they are way over built. You can pump the street engines way up in horse power and they will hold up. The engine on this bike was like the race engine. It has two cranks. It is basically two separate engines. You have a primary gear on the end of each crank that both connect to gear on the back of the clutch basket. The lower engine has the pipes coming out the bottom you can see in the pic. The upper engine has the pipes come out, the back and under the seat. That is why you see the bulge under the side covers. On hot summer days when ridding you would have to stand up on the pegs every so often and let you rear end cool off! Those after market Jolly Moto pipes had no heat shields on them and they would cook your back side. The transmission was also like a race bike. It was a cassette. You could undo the left side of the transmission cover and pull out all the gear shafts without pulling the engine from the frame.
I have had a lot of fast bikes over the years but this was the best. It might not of been the fastest, but it was the personality of the bike. That BIG two stroke power band. ( When it hit about 6000RPM you better be holding on tight), and the smell of a two stroke and the sound. This bike sounds like a swarm of angry bee's.