Hints and Tips - Identifying JAP Engines

 

Side Valve (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 50 70 x 88 mm.
N 200 cc. 55 x 83 mm MT 750 cc. v-twin 50 70 x 97 mm.
B 250 cc. 64,5 x 76 mm KT 980 cc. v-twin 50 85,7 x 85 mm.
A 300 cc. 70 x 78 mm KTCY 980 cc.(8/30) v-twin 50 85,7 x 85 mm.
I 350 cc. 70 x 90 mm LT 1100 cc. v-twin 60 85,7 x 95 mm.
K(Y) 500 cc. 85,7 x 85 mm DT 1323 cc. v-twin 60 90 x 104 mm.
L(Y) 550 cc. 85,7 x 95 mm
Overhead Valve (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 500cc side valve built in 1928


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