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 dates | |||||||||
| 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
