1972 Yamaha YZ642
1972 Yamaha YZ500
Jaak van Velthoven's 1972 YZ500 was also ridden by Torsten Hallman. The official code for the bike was YZ642
The 1972 YZ642 was a full 500cc motocross bike and it was Yamaha's 2nd version of a full 500. The first came along in 1971 and was a completely different design. There are no known examples left of the 1971 model. The 1972 version featured here, is one of only three examples in the world today. This bike was originally assigned to Belgium's Jaak van Velthoven and later was ridden by Torsten Hallman. The last time Torsten rode the bike, the throttle stuck wide open and Torsten was pitched violently over the bars. He vowed never to ride it again. All of the Team Yamaha factory riders preferred the 360 over the 500 as the 360 was much more tame and refined. The 500 was very unique in engine displacement and frame design. We will go over all of that in our feature when the bike is complete. Below are a few archive shots of the bike back in the day.
Jaak's YZ500 in the pits at the 1972 500 British Grand-Prix. The bike is in very similar condition today. Especially the tank. The engine is full sand cast and features a 4-speed gearbox.
On the trailer where it mostly stayed. Jaak prefered the YZ639 360 bike
Jaak's YZ639 was essentially the prototype for the 1974 YZ360. Note the left side rear brake pedal on Jaak's bikes.
Jaak van Velthoven in action on the YZ500 4-speed
Yamaha was really stepping out with a 500cc motocross bike in 1972