In the early years of motorcycle manufacturing, many manufacturers used bought-in engines for their motorcycles as the cost of developing engines was beyond the means of many of them. Of all the manufacturers of proprietary engines, possibly the most famous was J.A. Prestwich, otherwise known as J.A.P.
770cc JAP in the Ukraine
550cc single from 1922
Without the J.A.P. engine, many British motorcycle manufacturers would never have got off the ground and, over the years, J.A.P. supplied engines to Brough Superior, Triumph, AJS, Enfield, HRD-Vincent and Zenith, as well as manufacturers in France and Germany.
1911 ad
BSA single
JAP 350cc in France
The engine also saw service in cars such as the Morgan three-wheeler. The New Brough Superior Raises The Bar For Exotic Motorcycles, as well as in Formula 2 and Formula 3 racing in the 1950s.
1922, 250cc single
600cc
Ad from 1923
The versatility of J.A.P. engine design can be seen in their stationary engines, which have powered a wide array of industrial equipment such as generators, rotavators, water pumps, milking machines, hay lifts, and numerous machines in the agricultural industry.
1922, 350 crankcase
1922, 350cc single
1930s Speedway
During World War II, the company supplied close to one-quarter of a million petrol-powered engines in addition to millions of aircraft parts.
1922, 550cc single
JAP factory
1947, 125cc, two-stroke
--Sam Burns
Antique motorcycle curator
Bikernet.com™
1929 San Soup... 500cc
The extensive list of manufacturers which employed JAP engines includes:
Acme
AJW
Aliprandi
Alldays & Onions
Ambassador
Argentre
Ariel
Brough racer
Atala
Austral
Automoto
Cotton
AWD
Bown
Bücker
Hazelwood, check the belt...
Brough-Superior
Brown
Calthorpe
Chater-Lea
Clement-Gladiator
La Mondiale
Corah
Cotton
Coventry-Eagle
De-De
Dennell
DMW
Dollar
Matchless
Dunelt
Eysink
Favor
Fusi
Ganna
Grindlay-Peerless
Morgan trike
Hagon
Hazelwood
Imperia
Invicta
La Mondiale
Lady
Le Grimpeur
Lea-Francis
Majestic
1919 Excelsior-Henderson board-track racer
Matchless
Meray
MGC
Morgan
New Hudson
New Imperial
New Map
Nut
Acme
OEC
OK-Supreme
Omega
Onoto
Osa-Liberty
Radior
Rex-Acme
Rover
Rovin
Royal Enfield
Royal Ruby
San Sou Pap
Royal Enfield
Simoncelli
Soyer
Sparkbrook
Stylson
Terrot
Tornax
Trump
1913 Alldays
Ultima
UT
Verlor
Vindec
Wolf
York
Zenith
Sources: Graces Guide
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