Reverse-Cylinder Engine Designs
Their History
You don't need to know this, but it's pretty cool stuff; even in the world of motocross, everything that could be invented has been invented; and turned around backwards
The
2014 Yamaha YZ450F.
The reverse cylinder of the 2010-2014 Yamaha YZ450F and the just-introduced2014
YZ250F may seem incredibly
original, but that is not true—it is a very old idea. The MXA wrecking crew scoured our memories, and those of
our grandfathers, to come up with a fair-to-middlin’ list of reverse cylinder
engines. We promise you that there are many more reverse cylinder engines
produced over the years, but focused on the most significant.
1922
Opel 204cc Motoclub.
The first example we
found was the 204cc Opel Motoclub, It was a water-cooled, OHV, four-stroke with
the cylinder turned around backwards. It was produced from 1922 to 1925. The
Opel company would later specialize in automobiles.
1925
Orionette TS 246.
1927 Zachka helicopter.
Designed in
1927, Engelbert Zaschka's helicopter was a combination of an autogyro and
a helicopter. In appearance, the Zachka helicopter looks like a typical
airplane of the era, but the wing revolved around the fuselage of the plane.
His motorcycle engine was equally unique. Three years later, in 1925, the German-built Orionette produced
the 246cc TS model. The Orionette was a unique two- and four-stroke combined
design that used the backwards cylinder designed by Engelbert Zaschka.
1939
DKW SS250.
1934 DKW URe250.
One of the most famous reverse cylinder bikes of all-time
was the 1939 DKW SS250. This split-single engine design had two pistons, a
yoked connecting rod, a rear facing exhaust system and a single common
combustion chamber. DKW had a long line of reverse cylinder bikes starting with
the 1934 URe 250 and continuing on into 500cc versions.
1949
Honda 98cc Dream D. 
The first official production motorcycle by Honda was the 1949 Dream D. This
98cc two-stroke featured a reverse cylinder, two-speed transmission and
stamped-steel frame. It’s 50mm by 50mm bore-and-stroke engine pumped out three
horsepower at 5000 rpm. In 1951 Honda removed the reverse two-stroke engine and
put in a 146cc OHV four-stroke.
East
German MZ RE 125 road racer. .jpg)
Equally important in the timeline of backwards cylinders was the 1960 MZ RE125.
This East German road racer was designed by Walter Kaaden, the father of the
expansion chamber. Kaaden’s water-cooled, rotary-valve, reverse cylinder design
was copied by the Japanese when MZ’s Grand Prix rider, Ernst Degner, defected
from East Germany with a complete set of Kaaden’s secrets.
1965
Suzuki clone.
Degner defected from
East Germany while leading the 1961 FIM 125cc World Road Racing Championship
with only one race to go. Degner (with his wife and children) escaped from East
Germany in the trunk of a car. Degner immediately signed a contract with
Suzuki. According to sources, Degner arrived at the Suzuki factory in
Hamamatsu, Japan, under the pseudonym of "Eugene Muller" taking with
him some MZ parts (cylinder, piston, crankshaft and rotary-valve) plus some
blueprints. Degner reportedly shared most of Kaaden’s ideas with Suzuki. This
paved the way for the Japanese domination of small displacement motorcycle
racing in the following decades. The most notable Kaaden-clone was the 1963
Suzuki RT63 road racer.
Ernst
Degner (2) on the Suzuki RT63.
1960 Guazzoni Sportiva rotary-valve engine.
1960 Guazzoni 50cc Cadet road racer brochure.
Italian brand Guazzoni started making motorcycles in 1935, but hit pay dirt in
the 1960s with a line of 50cc, 100cc and 125cc rotary-valve two-strokes that
sold well in Italy. Very few Americans will remember the 1971 Guazzoni 125cc
Mattacross, but it was one of the lightest motocross bikes ever built. Guazzoni
went out of business in 1976 and founder Aldo Guazzoni died in 1978.
1965
CZ 50cc banana-frame road racer. 
A
maroon-tanked 1971 Jawa rotary-valve road racer. 
1968
Water-cooled, dry-clutch, rotary-valve, reverse-cylinder Tatran road racer.
CZ, Jawa and Tatran
reverse-cylinder road racers were all the same basic bikes and came from the
same factory from the mid 19670’s to the late 1970’s. The Tatrans were what the
CZ’s were called in international road races. If they were red/white or
blue/white, they were Tatrans, if they were silver, beige or maroon they were
Jawas.
1965
Bridgestone EJR-1 50cc water-cooled twin.
In the early Sixties, the Japanese motorcycle industry was going through a
tough period, and a number of the major manufacturers were destined to shut
down. Bridgestone was able to survive, and in fact benefited from an influx of
fresh engineers and designers (notably from Tohatsu) who transferred to
Bridgestone when their original employers went bust. The outcome of this was a
range of new models all powered by rotary-valve engines. The most successful
racing version was the 1965 EJR-1 50cc water-cooled twin. Bridgestone is named
after founder Soichiro Ishibashi (in English “ishi” translates to stone and
“bashi” means bridge).
Yamaha
twin-cylinder TZ250 road race engine with the carbs underneath.
Yamaha itself is no stranger to turning the cylinders around backwards. The
1988 TZ250U twin-cylinder road racer had the exhaust pipes in the rear and the
t
win carburetors in the front. The cylinders were laid down so radically, that the carbs were only inches above the ground and
inches behind the front tire.
The
ATK version of the Cannondale MX400.
The ill-fated, overweight, hard-starting, undersprung, unreliable 2001
Cannondale MX400 was the most notorious reverse cylinder design ever made.
After investing $80 million in its failed motorsports venture, bicycle
manufacturer Cannondale filed for bankruptcy in January 2003. ATK bought the
rights to the engine and have continue to produce bikes with the reverse
cylinder design for awhile.
The
Synergy Q450.
The
Q450 engine.
In 2004 the Synergy Motorsports Q450 showed a
reverse cylinder, 445cc, fuel-injected, electric-start, carbon fiber-framed
four-stroke at the Indianapolis Interbike and Cologne Intermot shows. The bike
never saw production and was mysteriously stolen from the show floor in Europe.
The
Ossa TR280 trials bike.
And finally, in 2010 Ossa revealed a prototype 272cc reverse
cylinder, two-stroke engine. It will be used in the TR 280i trials bike. The
fact that the Ossa TR 280i has an electronic-injection system has enabled
Ossa's engineers to redistribute various parts without being constrained by the
position of the traditional carburetor. "Sometimes the injection system
has been put in the same place as the carburetor would have gone, with the fuel
tank at the top of the bike, without considering the option of finding a new
position for it. Ossa factory let me start from scratch and that was a
determining factor in taking on this project," says Ossa designer Josep
Serra.
The
Ossa 250i/300i two-stroke.
The
Ossa expansion chamber has a snail-like design. The air filter is in the white
airbox behind the radiators.
Following the introduction of Ossa TR 280i, Ossa came back two years later with
the unique Ossa 250i/300i enduro bike. It not only had a reverse engine, but
was a fuel-injected two-stroke. The world is still waiting for serious
production models.
The
2014 Yamaha YZ250F engine.
So you see, reverse cylinder bikes are not the sole
possession of any manufacturer, but have a long and varied history.
