WALTER TYPE M
How the Walter Type M went from aircraft engine to army dispatch bike to racer
Started as an aircraft engine and ended up as a racing motorcycle
IN THE EARLY 1920s British Army dispatch riders were using 550cc side-valve Triumph singles or 350cc Douglas flat twins while German soldiers rode little NSU four-strokes or Puch two-strokes. If they knew what the Czech military were about to get their hands on, Tommy and Fritz would have been green with envy because the Walter was an advanced unit-construction, transverse V-twin with an overhead-valve layout pinched from an aircraft engine.
In 1922 the Walter car and motorcycle factory in Prague started work on a five-cylinder radial engine that could be used in training and sports aircraft. With a capacity of 5200cc and vertical overhead valves operated by long pushrods, power output was 60hp. After flying tests in an Avia monoplane, the rotary engine went into production. It must have impressed the Czechoslovakian Army, because the following year they asked the Walter factory to design and build an advanced motorcycle for its dispatch riders.
As car manufacturers it was a no-brainer that the new motorcycle would have unit construction for the engine and gearbox. The Prague engineers took one look at the radial engine and saw the cylinders and heads for a 45° V-twin. These would be mounted transversely on the crankcase to get the maximum benefit of the cooling air. With a bore and stroke of 75 x 85mm, the Walter Type M would have a capacity of 750cc.
While most motorcycles of the time used total-loss oiling, the Czech bike would have an advanced dry sump and circulating lubrication system. A multiplate
‘IN SPITE OF ITS SUCCESS, IT WAS THE LAST MOTORCYCLE TO CARRY THE WALTER NAME’
clutch transferred power from the crankshaft through a splined shaft and a crown wheel and pinion to the threespeed gearbox. A hand-change lever to change ratios was mounted on the right. Surprisingly, a chain was chosen for the final drive.
The engine was clamped in a sturdy double-cradle brazed lug frame, with trailing link fork that looked like an American import. There was a single carburettor, and the exhaust pipes were joined in an alloy expansion box that silenced the V-twin to a soft whisper.
Ready for action, the new Walter motorcycle weighed about 145kg. With a top speed of 100kph (62mph) and using only 4.5 litres of petrol every 100km (62mpg), the Type M easily met the Czech Army specification, even if there was no front brake.
As the Walter factory boasted a rich racing heritage, there was no way that the Type M was going to be confined to army duties alone – and one was soon prepared for racing. Removing the mudguards, carrier and toolboxes and using straight-through exhaust pipes saved quite a few kilos.
A forward-facing carburettor bellmouth let the engine breathe cooler, denser air but any hopes of forced induction increasing power would have been dashed as the Walter would need to be travelling at about 300kph (186mph) before it would have any effect.
With upside-down handlebars, a lowered and unsprung saddle to put the rider into a racing crouch, along with a scissor-type friction damper from the race cars to stiffen up the forks, ace riders like Vaclav Liska must have hoped for smooth tracks. The results were encouraging enough for a full race version to be built in 1925 – the Type M-922.
Instead of cast-iron barrels and heads, the M-922 would have big-bore steel liners with alloy muffs, and bronze heads with hemispherical combustion chambers. While the modified army bike had the inlet and exhaust rocker arms supported on a single spindle running across the cylinder head in line with the frame, there would now be separate spindles with rigid supports running at right angles to the frame. Separate exhaust pipes were tucked under the frame tubes.
The Walter race engineers sent to England for George Dance knee grips and a special carburettor – the Binks Rat-trap. For flat-out acceleration there was nothing better in the 1920s, and the M-922 soon notched up a string of victories.
But in spite of its success, it would be the last motorcycle to carry the Walter name. The Praguejinonice factory was too busy making luxury cars, heavy trucks and aircraft engines to devote precious resources to motorcycle production.
Walter would go on to make jet and turboprop engines until they were taken over by General Electric Aviation in 2008. If only they’d devoted a corner of the factory to motorcycle production, today you could have been choosing between a BMW, a Guzzi or a Walter.