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J.A. Prestwich Motorcycles

J.A.P. Engine Numbers

JAP Logo

This page is archived (with minor modification) from the original site by Martin Schenker

Identify a JAP engine


Side valves (SV) :
V 175 cc. 60 x 62 mm. U 600 cc. 85,7 x 104 mm.
Z 175 cc. 55 x 73 mm. GT 680 cc. v-twin 50deg 70 x 88 mm.
N 200 cc. 55 x 83 mm. MT 750 cc. v-twin 50deg 70 x 97 mm.
B 250 cc. 64,5 x 76 mm. KT 980 cc. v-twin 50deg 85,7 x 85 mm.
A 300 cc. 70 x 78 mm. KTCY 980 cc.(8/30) v-twin 50deg 85,7 x 85 mm.
I 350 cc. 70 x 90 mm. LT 1100 cc. v-twin 60deg 85,7 x 95 mm.
K(Y) 500 cc. 85,7 x 85 mm. DT 1323 cc. v-twin 60deg 90 x 104 mm.
L(Y) 550 cc. 85,7 x 95 mm.

Over head valves (OHV):
HO 175 cc. 53 x 78 mm. KOC 500 cc. sports 85,7 x 85 mm.
TO 200 cc. 57 x 78 mm. KOR 500 cc. racing 85,5 x 85 mm.
PO 250 cc. 62,5 x 80 mm. JOR 500 cc. racing 80 x 99 mm.
POR 250 cc. racing 62,5 x 88 mm. PTOR 500 cc. racing v-twin 62,5 x 80 mm.
NOR 250 cc. racing 65,5 x 74 mm. GTO 680 cc. racing v-twin 70 x 88 mm.
BOR 250 cc. TT racing 64,5 x 76 mm. KTOR 980 cc. racing v-twin (8/45) 85,7 x 85 mm.
SOC 350 cc. sports 74 x 80 mm. KTO 980 cc. (8/45) v-twin 62,5 x 80 mm.
SOR 350 cc. racing 70 x 80 mm. JTOR 998 cc. racing v-twin (8/50) 80 x 99 mm.
IOR 350 cc. racing 70 x 90 mm. JTO 998 cc. touring v-twin 80 x 99 mm.
SOS 350 cc. grass track 74 x 80 mm. JTOS 998 cc. sprint v-twin (8/80) 80 x 99 mm.
JOS 500 cc. 80 x 99 mm. W/W 1100 cc. racing v-twin ? x ? mm.
YTO 500 cc. v-twin 60 x 88 mm.

Production date:
1920 1921 1922 1923 1924 1925 1926 1927 1928 1929
P N E U M A T I C S

1930 1931 1932 1933 1934 1935 1936 1937 1938 1939
W H Y Z D R V F O G

As an example: An engine with the letters KY/C on the crankcase is a 500 ccm sv, built in 1928

Two-stroke JAP numbers include F2UH, a 3 speed unit-construction single with iron barrel and head.

This page was copied and converted to english from the Danmarks Veteran Motorcykleklub
There is another very useful page with similar information on JAP Engine Numbers at http://www.donaldantiquerototillers.com/JAPEngineChart.htm

Another source of JAP serial numbers: 
http://www.vfv-motorrad-forum.de/

The original version of this page saved from http://web.archive.org/web/20041010132218/http://www.mpimg-berlin-dahlem.mpg.de/~schenker/jap.htm

Sources:



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