In the studio: CZ 250 dohc prototype

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In the studio: CZ 250 dohc prototype
www.bilski-fotografie.de

In the studio: CZ 250 dohc prototype

In the studio: CZ 250 dohc prototype

In the studio: CZ 250 dohc prototype

In the studio: CZ 250 dohc prototype

25th pictures

In the studio: CZ 250 dohc prototype
www.bilski-fotografie.de

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CZ 250 dohc prototype.

In the studio: CZ 250 dohc prototype
www.bilski-fotografie.de

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CZ 250 dohc prototype.

In the studio: CZ 250 dohc prototype
www.bilski-fotografie.de

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A vertical shaft drives the two camshafts via four spur gears. Drive of the oil pump and ignition magnet under the cover leading upwards at an angle

In the studio: CZ 250 dohc prototype
www.bilski-fotografie.de

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CZ 250 dohc prototype.

In the studio: CZ 250 dohc prototype
www.bilski-fotografie.de

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Good to see: The exhaust manifold, which is flanged at an angle for reasons of space, and the drive for the rev counter.

In the studio: CZ 250 dohc prototype
www.bilski-fotografie.de

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CZ 250 dohc prototype.

In the studio: CZ 250 dohc prototype
www.bilski-fotografie.de

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If necessary, the primary drive can be lubricated via the oil reservoir with shut-off valve placed in front of the cylinder.

In the studio: CZ 250 dohc prototype
www.bilski-fotografie.de

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CZ 250 dohc prototype.

In the studio: CZ 250 dohc prototype
www.bilski-fotografie.de

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CZ 250 dohc prototype.

In the studio: CZ 250 dohc prototype
www.bilski-fotografie.de

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Simplex drum brakes at the front and rear made of electron casting (Ø 220 mm) with riveted steel drum.

In the studio: CZ 250 dohc prototype
www.bilski-fotografie.de

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CZ 250 dohc prototype.

In the studio: CZ 250 dohc prototype
www.bilski-fotografie.de

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As of the 1950s: Smiths tachometer from non-socialist countries and an adjustable steering damper on the CZ.

In the studio: CZ 250 dohc prototype
www.bilski-fotografie.de

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CZ 250 dohc prototype.

In the studio: CZ 250 dohc prototype
www.bilski-fotografie.de

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CZ 250 dohc prototype.

In the studio: CZ 250 dohc prototype
Private

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A historical photo of CZ works pilot Stanislav Malina on the 850 prototype with dohc cylinder head at a national championship run in 1955.

In the studio: CZ 250 dohc prototype
www.bilski-fotografie.de

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CZ 250 dohc prototype.

In the studio: CZ 250 dohc prototype
www.bilski-fotografie.de

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CZ 250 dohc prototype.

In the studio: CZ 250 dohc prototype
www.bilski-fotografie.de

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CZ 250 dohc prototype.

In the studio: CZ 250 dohc prototype
www.bilski-fotografie.de

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CZ 250 dohc prototype.

In the studio: CZ 250 dohc prototype
www.bilski-fotografie.de

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CZ 250 dohc prototype.

In the studio: CZ 250 dohc prototype
www.bilski-fotografie.de

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CZ 250 dohc prototype.

In the studio: CZ 250 dohc prototype
www.bilski-fotografie.de

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CZ 250 dohc prototype.

In the studio: CZ 250 dohc prototype
www.bilski-fotografie.de

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CZ 250 dohc prototype.

In the studio: CZ 250 dohc prototype
www.bilski-fotografie.de

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CZ 250 dohc prototype.

In the studio: CZ 250 dohc prototype
www.bilski-fotografie.de

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CZ 250 dohc prototype.

counselor

technology & future

In the studio: CZ 250 dohc prototype

In the studio: CZ 250 dohc prototype
Urgent messenger from the East

Content of

CZ only built two copies of this beautiful 250cc factory prototype with a dohc cylinder head in 1955. Restored true to the original, one of those ultra-rare racers is honored here.

Uli Holzwarth

08/04/2016

Impressive racing motorcycles were also built beyond the Iron Curtain. Especially with Ceská Zbrojovka, or CZ for short, in Strakonice, Czechoslovakia. Even before the war, Jaroslav Walter, son of the Czechoslovak motorcycle pioneer Josef Walter, designed his first ohv racing engine with 250 cc.

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After the war and the nationalization of his father’s gear factory in 1948, Jaroslav Walter received the green light to set up the CZ racing department. On the basis of his ohv engine, he constructed versions with 250 and 350 cm³ from 1950, which brought in numerous victories in national races. Encouraged by this, CZ entered the 125cc series in 1952 with a dohc engine with a vertical shaft drive newly designed by Walter. With considerable success, even with sporadic missions in the west. And at the 1952 Czechoslovak Grand Prix, which was not yet part of the World Cup, there were even three CZ pilots on the podium!

The CZ 850 dohc looks harmonious, as if it were made from one piece

Further successes of the 125cc racing machines, including a victory in Sweden in 1954, left little room for further development of the aging 250cc, internally known as the Type 850, although Jaroslav Walter had already started with it in 1952. For the 1955 season, two factory racing machines of the type 850 therefore only needed a new double-cam cylinder head, with which the CZ factory driver Stanislav Malina was able to achieve some national successes at the time.

Our photo model is one of these two transitional models – the 250cc racing machine completely redesigned by Jaroslav Walter with the type designation 853 was only finished at the end of 1955. Compared to the single-cam control of the aged base, the dohc head with the four spur gears driven by a vertical shaft was much larger, which is why the carburetor and manifold were flanged on at an angle. Which doesn’t harm the aesthetics of this machine in the least. On the contrary, the CZ 850 dohc looks coherent, as if it were made from one piece. One more reason why the current owner has bought this exotic motorcycle. He is enthusiastic about the little-known racing machines of the Eastern Bloc. In this 250cc CZ racing machine he sees a “unique prototype with a beautiful line that is very interesting both in terms of technology and history”.

Original magnesium case still available

The reconstruction was in the hands of Libor Kamenicky, chairman of the Czech Classic Motorcycle Association, and Olda Prokop. Prokop, a collector of Jawa and CZ factory machines, is in possession of the original CZ construction drawings.

A stroke of luck, because the engine housing could be reproduced with the help of complex aluminum casting molds. The original housing made of magnesium is still there, but today would make any demonstration drive a risky undertaking because of the now brittle cast material. Because it should continue to drive, the CZ. And show what impressive constructions were created behind the Iron Curtain back then.

Technical data CZ 250 dohc (type 850)


In the studio: CZ 250 dohc prototype


www.bilski-fotografie.de

If necessary, the primary drive can be lubricated via the oil reservoir with shut-off valve placed in front of the cylinder.

Engine: Air-cooled single-cylinder four-stroke engine, two valves, via vertical shaft, spur gears and two overhead camshafts
actuated, bore 63 mm, stroke 80 mm, displacement 249.4 cm³, compression 8.4: 1, approx. 35 hp at 9000 / min, an Amal TT carburetor, dry clutch, four-speed gearbox, chain drive

Landing gear: Double loop tubular steel frame, hydraulically damped telescopic fork, two-arm swing arm with two hydraulically damped spring struts at the rear, simplex drum brakes at the front and rear, Ø 220 mm, tires 2.75-19 at the front, 3.00-19 at the rear, dry weight approx. 115 kg, tank capacity 23 l

Top speed: 170 km / h

Construction year: 1955

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