Decarbonising The Cylinder Head - Combustion Chamber; Piston And Rings; Big End Bearing Inspection - Royal Enfield Bullet Workshop Manual

5. Decarbonising the Cylinder head
-
Combustion Chamber
6. Hston and Rings
If the piston rings are in good condition they can be put back, taking care to fit them in their
original grooves and the same way up. If the fitlgs show bmwn or black patches or if their
gaps, are more than specified senice limits (Page 79), when in position
in
the barrel, new rings
should be fitted. The correct gap for new rings is given in the technical specifications (pages
6 13 8
)
for 350 and 500cc. The gap should be measured
in
the least wdrn part of the cylinder
which will be found a t the top or bottom of the bore.
Only For 350cc:
The original size of the cylinder bore is 2.751" (69,875rnm). If the wear a t any point in the
bore exceeds .008" the cylinder should be rebored to .020" and
an
oversize piston fitted. (It
should be rebored to .040" &er a further .008"Wear). Piston sizes available are . 0 2 0 and .040"
oversize.
The original side clearance between the piston rings
CRANKSHAFT BIG END BEARING
and grooves
is
.003". If the grooves show
a
wear of .005"
the piston should be replaced.
7. Big end bearing inspection
Examine the condition of
ttle
big end while the piston
is
removed. About .010"
-
.026" end float is permissible and
it will be possible to rock the connecting rod slightly. The
big end has a floating bush with a n original clearance of
approximately .003" However, if a DEFINITE u p and down
play can be felt, engine should be stripped further to have
the big end renewed.