HO means Houzé - Offenstadt, and if the second name is very well known in the motorcycle world, the first probably does not
ring a bell. In fact, although not belonging to the world of racing, Bernard and Michel Houzé were very quickly seduced by
Eric's ideas and they decided to finance the operation by devoting a large budget to the creation and development of the HO.
They deserved, therefore, to be associated with the motorcycle's surname.
The 497cc engine is conventionally powered by two 32 millimeter Gurtner carburettors and two 28 millimeter carburetors in an
additional intake. The cylinders were designed by Eric Offenstadt and produced by a company specializing in high precision
work, FIMA, a company which had already made the cylinder heads of the 12-cylinder Matra and therefore had serious
references. The gearbox uses Yamaha components, but a number of special gears had to be made, while the water pump also comes
from a TZ, and the clutch uses discs from the same machine. A Femsa ignition equips the HO, while the crankshaft comes from
Kawasaki. Single-segment Mahle pistons sit in the cylinders. The most revolutionary
aspect of this engine is that it uses four Gurtner carburetors. Each cylinder has a double intake, seven
transfers and an exhaust, for a total of ten "holes". The classic rear intake is carried out through the piston skirt while
the additional front intake is equipped with an anti-backflow system.
The SMAC alloy monocoque frame has the particularity of being split into two parts along the median axis of the motorcycle. Note that the machine can carry 25 liters of fuel,
including the 9 liters in the hull.
The wheels are six-spoke SMAC magnesium with Michelin tires. The brakes are Brembo calipers and discs with a diameter of 255
millimeters in the front and 200 millimeters for the small rear disc. Two special Carbon oleopneumatic shock absorbers
special made for this bike sit at the back. They perform in the most efficient way, without it being
necessary to intervene in the adjustment.
At the front the bike has an ultra distinctive superradical trailing-link suspension with a Carbon shock absorber adjustable in pre-compression and hardness. A second updated version of this bike is known as the But 500.
Characteristics
Engine
Type 500 HO 2 cylinder
Watercooled 2-stroke
Bore and stroke: 71 x 62.8
Compression ratio: 8.5 to 1
Power: 80 hp at 10,500 rpm
Power supply: dual intake: 2 carbs per cylinder
Rear: diameter 32 Gurtner
Front: diameter 28 Gurtner
Ignition: Femsa
Chassis
Frame: aluminum monocoque
Front suspension: 1 of Carbon adjustable. Travel: 15 cm
Rear suspension: 2 Carbon oleopneumatic. Travel: 13 cm
Front brake: 255 mm diameter discs
Rear brake: 200 mm diameter disc
Front wheel: 3.50 x 18
Rear wheel: 3.50/5.10 x 18
Performance: 272 km/h at 9700 rpm
Weight: 115 kg
For more pics see
Want to know how it sounds see
The Reimo GTR900, made by Reimo Suzuki from Germany, this was their top model. Reimo was founded by Wolfgang Reinhard and sidecar GP racer Horst Owesle. The company was well known for their tuning and special parts for the Suzuki GT750. Tank seat combi's, special exhausts like 3into1's and expansion pipes, wheels, swing arms, shocks and a chain protector. Reimo still exists today and even now they make a TR750 replica.
This Spondon RGTZ500 is a rather special bike, between 1989-1992 it was raced by Gerhard Vogt with a Suzuki XR71 V4 engine in it. This was the only private XR71 at that time. When Gerhard stopped racing the rolling chassis was sold to Jürgen Plaschka who mounted a Suzuki RGTZ500 square four engine in it with Bartol Yamaha 4dp cylinders, Mikuni TM35 carbs and a GHN gearbox. Jürgen raced it between 1994-1999 in the German 500cc championship and was often the best Suzuki between the ROC and Harris Yamaha's. 
In 1985 MBK Innovation with Jean Michel Basset in the lead made a very special machine for Paris Dakar around a Yamaha RD350LC engine. The project was all about achieving a particularly high weight to power ratio, and the MBK engineers definitely succeeded. On the scales the bike weighed only 135 kg and had a power of 65 HP at the wheel! To get an idea and a comparison, in those years the BMW GS was the fastest with a top speed of 180 km/h and the most powerful with approx. 80 HP with a 1050 cc engine. The engine of the Yamaha RD350LC offered the power necessary to reach 145/150 km/h on the sand. The second objective was to give its riders, Patrick Vallet and Pierre Marie Poli a light and easy to handle motorcycle. For this purpose, aluminum was used extensively for the creation of the oversized radiator, air box, fuel tank, oil tank (remember that the engine ran on a 3% mixture) and water tank. Achieving 135 kg dry weight was a high-level engineering feat for its time. But as history shows, numbers and ideas on paper don't go well with the harsh world of racing. Unfortunately the MBK Innovation 350 did not arrive in Dakar with any of the drivers.
The Spondon XR45 of Theo Louwes. In the last racing days of the Suzuki RG500 different manufacturers made deltabox frames. I made a photo set, Bakker, Spondon, VRP, GPA, Harris and Golinelli, I also included the modified street frames. 
Rob Bron on the Bakker HRD GTR750 at Daytona in 1975.
Beautiful YZR500 replica seen at the CRT two stroke track day, Assen 7 Oktober 2023.