Here we have a very special bike made by Dan Hanebrink! The description on the Hanebrink site (no longer there) pretty much sums it up:
"In 1971 “Cycle News” publisher Chuck Clayton asked Costa Mesa, California engineer Dan Hanebrink to sketch a futuristic machine of the eighties for a front page Christmas issue of the newspaper. From this sketch Hanebrink developed his ideas and the result, two years later, was the Monotrack Experimental. This design accounted for a large number of firsts in motorcycle engineering. The monocoque chassis was made from magnesium plate and a three-cylinder, rubber-mounted, two-stroke Kohler snowmobile engine provided power to the belt-driven torque converter. Drive to the rear wheel was also by belt. Hanebrink produced the 16-inch cast magnesium wheels on which Goodyear racing tires were mounted. The suspension had no springs, but relied on air and oil damping. The circular component on the fork bottom and rear strut contains a central neoprene diaphragm, which separates the oil and air. In use, the oil in the suspension struts compresses the air under load, allowing 41/2 inches of travel in the front forks and 4 inches in the rear."
Dan Hanebrink has been building quite a few interesting vehicles over the years including the “Ice Bike” used in a bicycle trip to the south pole, which is now his Extreme Terrain Bike which can be used on sand, snow or wherever else a regular bike can’t go. Dan has done a little downhill bicycle racing, too, and of course there is the motorcycle business.
Dan Hanebrink died at the age of 80 on 29 December 2018.
For more pics see
Barry Sheene on the very special Hi-Tac Suzuki 500 two stroke twin. The Hi-Tac was Peter Inchley's (ex-Norvil chief) project, started in 1972. He saw that water cooling was desirable for two strokes and designed a thermo-siphon kit for the T500 (before Suzuki's own watercooled TR III). 
This amazing assemblage is the V12 Rotorvic two stroke which appeared in British club racing in 1965, powering a specially modified Lotus 23 sports car. It consists of six Ariel Arrow two stroke motorcycle engines disposed at an included angle of 90-degrees and driving the central shaft. Transmission was via a Hewland five-speed gearbox and the engine was cooled via huge air-scoops in the body panelling. This 1482cc V12 made a ferocious noise and it was almost impossible to tell it was misfiring on one or two cylinders. It produced 220bhp at 10000RPM. The creator was R.V. Marchant and the driver was Bill Hill.
Updated my König photo set with a lot of new pics. König was the manufacturer of the great four cylinder boxer two stroke outboard racing engines. These engines were also used in the 500cc motorcycle world championship by Kim Newcombe.
Through the years I have seen a lot of replica bikes using RG400 and 500 engines, this must be the most special one! It is a Suzuki RZ63 replica, also known under the infamous name the "Whispering Death". It uses an RG400 engine in a TR500 frame. 
Here we have some nice pics of a Nico Bakker Suzuki RG500. As far as I can see it has a heavily modified RG500 Gamma engine with dry clutch and RGB500 carbs. 
In 1997 Kenny Robert’s team switched from Yamaha YZRs to a bike of their own design. Based on the same principle behind the Aprilia RSW500 – that is taking advantage of the lower minimum weights for 2 or 3-cylinder bikes, Roberts and his main team engineers Mike Sinclair and Warren Willing, together with Tom Walkinshaw Racing, came up with a V3 design that was about the size of a 250cc class bike. It weighed just over 135kg and made around 160hp. The first model (Modenas KR3) suffered from engine vibration problems so a redesign was instigated. The name was then changed to Proton KR3, to mirror the new team sponsorship. On this bike Jeremy McWilliams set pole on the 2002 Australian GP, the last time a two-stroke achieved this feat.