Yvon DuHamelís KR750 w/ Parallelogram Linkage Suspension
The Kawasaki parallelogram was originally redesigned
by two U.S. R&D engineers, Jerry Marcel and Hank Hosoi, in late 1973. The
original concept came from the equal length F arm front and rear suspension
components of a 1930's era racing car suspension. There were a couple of
different Kawasaki versions, the one in the pic is one of the latter ones. There
weren't many built, only 6 or so total between roadracing and motocross/off road
racing, that I am aware of.
All these chassis were built and handled by R&D, with the other parts (engines, electronics, front ends, wheels, etc.) loaned from the various racing departments.
The nickname for this suspension was "FUBAR". You may add any meaning you wish to that name, but it means exactly what FUBAR means. f..up beyond all recognition/repair.
They were tested on the bike above, which was a Team Kawasaki bike only, and a couple of KR250's, and Brad Lackey's KX450 as well. Jimmy Weinert also ride the KX version a bit, in testing only. I think Walt Axthelm
also had one of the KX's for testing in off-road/six days/Baja use too.
The concept was to create a swing arm setup that didn't move the rear axle from loose to tight to loose on chain tension, and to make for a much more stabile rear suspension operation, like a car suspension works a tire straight up and down, without deflection. The parallelogram was somewhat successful, but considerably heavier than what was desired.
Japanese manufacturers came up with something much better soon after the FUBAR program was scrapped by the U.S. engineers, the single (mono) shock and braced swing arm, aiding suspension, but not chain tension issues. Most of the Team motocross bikes with conventional single swing arms, were fitted with Cancilla chain tensioners, and that took care of the chain issues for them.
The most unique of these parallelogram frame setups were the two H2R ones built for testing in late 1973. One was a short chassis, the other was patterned after the longer Talladega chassis.
I know of only one chassis set that got out of Kawasaki R&D. I would hope there are a couple of them out in the private sector today, be nice to see another one.