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The Drkosch DR500

Jan Friedrich Drkosch of Bohemia (b.1913) had been a successful racer in Czechoslovakia. After WWII he moved to Germany where he worked as head of design with Adler. He developed the front suspension of the MB250 and was responsible for the chassis of the 1954 RS250. German designer Otto Lantenhammer developed his tuning skills under the tutelage of Jan Friedrich at Adler.

Heralded as the machine to beat the super quick JAP's and Jawa's in 1,000 metre racing, The DR500 was a single cylinder of 498.5cc with a high lift camshaft.

Initial tests indicated it exceeded 8,000rpm and claimed 70bhp.

The engine was developed by Drkosch whilst working with the company Wernecke-Zahndader-Getriebe, and is also referred to as the DR500 Wernecke. Some 20 lbs lighter than a JAP, but with the same stroke 84 x 90, it was hoped to be extremely competitive. The cylinder head was almost identical to that of an HRD Vincent and embodied all the best aspects along with a few refinements.

There was no magneto as such. The motor was timed from the flywheel with an electronic receiver inside the crankcase to pick up the pulse as used in some road racing engines at that time.

The earlier models had 2 spark plugs, whilst the later types came with only one spark plug.

The colour photo is from a longtrack machine with the 2 spark plug type of engine. The frame is a S.G.M. (Sepp Giggenbach from Muhldorf) Germany.

Type: 500 cc single-cylinder four-stroke speedway
racing engine, Type DR-500, 84 mm/90 mm bore / stroke.
Capacity: Cylinder volume 498.5 cc
Compression: 14:1 - exclusively run on methyl alcohol. Engine power 60 HP at 6,800 RPM, maximum speed 8,000 RPM
Carb: 35 mm DELLORTO racing carburettor
Ignition: BOSCH high-tension condenser magneto ignition
WERNECKE Duplex rotary piston oil pump, with patentable adjustment, high-performance valves with new type of springs - patentable Overhead camshaft, valves operated by push rods
Valve clearance control by new method of eccentric adjustment. New method of ignition timing adjustment (ignition control), patentable Crankshaft housing and rocker box cast of Electron.
Cylinder of aluminium with built-in barrel of cast material
Cylinder head of cast steel, 2 spark plugs
Weight: approx. 24 kg (53 lbs).

N.B. This page includes information not in the original archive.

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