Friday, February 23, 2024

Offenstadt 500 HO

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

Thursday, January 25, 2024

MBK RD350 Paris Dakar

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.
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Saturday, December 23, 2023

Deltabox Suzuki RG500's

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. 
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Thursday, November 16, 2023

Nico Bakker GTR750 Suzuki's

Rob Bron on the Bakker HRD GTR750 at Daytona in 1975.
Here we have all the Bakker GTR750's at one spot. The HRD ones have a horizontal monoshock, the other 3 have a vertical mounted shock. All the frames still exist. The Rob Bron bike was found a few years ago and is perfectly restored by the current owner.

Saturday, October 14, 2023

CRT two stroke track day Assen 2023

Beautiful YZR500 replica seen at the CRT two stroke track day, Assen 7 Oktober 2023.
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For a vid of the YZR500 replica see

Sunday, September 17, 2023

Classic GP Assen 2023

Kevin Schwantz his Lucky Strike RGV500 seen at the Classic GP at the TT circuit Assen September 2023. 
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Saturday, August 12, 2023

De Jager 500 boxer

The Dick de Jager 500cc four cylinder boxer two stroke is a very rare beast. As far as I know there exists only one engine. The König crankcases are known for weak casting and prone to crack. So de Jager decided to make a beter crankcase, the barrels are from Yamaha and the crank is a modified König one. The engine delivers 111 hp. Owner Luc de Smet from Belgium still races it at classic meetings with his female teammate Zoë Beun.
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