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AJS/M SINGLE PISTONS
A note on GPM pistons: the size indicated is the bore size of the barrel. GPM pistons are slightly undersize to this bore. If you race the bike or put it to heavy use the bore may be a touch bigger. Also use SAE50 oil.
!

350CC PISTON 1949 UP
ZGPM6916
!
GPM pistons are slightly undersize to the nominal bore.

350CC PISTON > 1949
ZGPM6920
!

CYLINDER LINER 350cc
ZGPM6920
!

Inner diameter 69mm, length 162mm.
Only a few left.

CS 500 PISTON
ZGPM862A
!

All in weight 717gr. for the STD size, so you'll have to grind some flesh away.

GENUINE WELLWORTHY +020 PISTON EARLY 350
WP339
!
New old stock, still covered in grease.
These will ONLY fit 1940-1948 models. (SMALL CYLINDER HEAD)
Only a few available

PISTON AJS/MATCHLESS 500CC SINGLE
ZJP680
!
1949 up 500cc singles (BIG CYLINDER HEAD)
Compression ratio 7.2:1
Compression height 46.03mm
Made by JP in Australia