A.J.S. 16MS, Instruction Book

Page: 32 / 94

Remove
One gudgeon pin circlip. It is immaterial which circlip is removed. Use special pliers
included in tool kit.
Gudgeon pin by pushing, it out of piston.
Take away piston.
NOTE—The gudgeon pin is an easy sliding fit in both piston and connecting rod small-
end bush.
Rings may be removed from a piston by " peeling off " with a knife, or by
introducing behind the rings three pieces of thin steel spaced at 120° from each
other and then sliding off the rings. (Do not scratch the piston.)
TO REPLACE THE PISTON AND CYLINDER BARREL
All parts must be clean.
Place rings on piston, scraper first then the two compression rings. On all models the
top compression ring is chromium plated.
These chrome plated rings have a slightly tapered exterior and when new are clearly
marked with the word TOP on one side to indicate assembly position. After use this
word tends to become indiscernable, but over a large mileage the assembly position can
be determined by brightness of the edge contacting cylinder wall. This bright edge is
the lower one. When as the result of wear, contact with the cylinder wall appears
uniform over the whole width of the ring, it is then immaterial which way round it is
re-fitted.
Smear gudgeon pin with engine oil.
Refit piston by :
Introduce piston over connecting rod, so that slit in piston faces to the front of the
machine.
Introduce gudgeon pin in piston and pass ft through connecting rod small-end bush and
centralise it.
Re-fit circlips. (Use special pliers). Use rotary action when bedding circlips in their
grooves and make sure each circlip lies snugly in its groove. This is essential otherwise
considerable damage will result.
Re-fit cylinder barrel by :
Take new cylinder base washer. Coat one side with liquid jointing compound and
apply it to cylinder base.
Smear cylinder bore and piston with clean engine oil.
Space piston rings so that the gaps are evenly spaced at 120° to each other.
Gently fit barrel over piston and carefully compress each ring in turn, with the fingers,
as it enters the chamfered mouth of the barrel.
Remove rag from crankcase throat.
Replace cylinder barrel holding down nuts, screwing each down, in turn, bit by bit, till
all are fully home.
CAM CONTOUR
On the flanks of the cams are quietening curves which are very slight inclines from the
base circles to the feet of the humps.
Therefore, it is necessary to ensure the tappet ends are on the base circles when checking
valve clearances and valve timing.
It is for this reason valve clearances must be checked when the piston is at the top of its
compression stroke, at which position both tappets are well clear of the quietening
curves.
30
www.ajs-matchless.info