Explorer GT 50, Service And Maintenance Manual

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42
If the largest reading at any portion of the staightedge excees
the limit, rework the surface by rubbing it against emery paper
laid flat on the surface plate in a lapping manner. The surface
must ge smooth and perfectly falt in order to secure a tight
join: a leaky joint can be the cause of reduced power output
and increased fuel consumption.
CYLINDER
Decarbon exhaust port and upper part of the cylinder, taking
care not to damage the cylinder wall surface. The wear of the
cylinder wall is determined from diameter reading taken at
20mm from the top of the cylinder with a cylinder gauge. If
the wear thus determined exceeds the limit indicated below,
rework the bore to the next oversize by using a boring machine
or replace the cylinder with a new one. Oversize pistions are
available in two sizes: 0.5mm and 1.0mm.
(cylinder gauge)
service limit
᧶
40.075mm(1.5778in)
after reworking the bore to an oversize, be sure to chamfer the
edges of ports and smooth the chamfered edges with emery
paper. To chamfer, use a scraper, taking care not to nick the
wall surface
.
127(᧶
Minor surface flaws on the cylinder wall durto seizure or
similar abnormalities can be corrected by grinding the flaws
off with fine-grain emery paper. If the flaws are deep grooves
or otherwise persist, the cyliner must be reworked with a
boring machine to the next oversize.
PISTON
cylinder and piston clearance
cylinder –piston clearance is the difference between piston
diameter and cylinder bore diameter. Be sure to take the maked
diameter at right angles to the piston pin. The value of
elevation
ż
,A is prescribed to be 20mm from the skirt end.
(micrometer)
service limit
᧶
39.885mm(1.5703in)
As a result of the above measurement, if the piston-to-cylinder
clearance exceeds the following limit, overhaul the cylinder
and use an oversize piston, replace both cylinder and piston.
The measurement for the bore diameter should be taken in the
intake-to-exhaust port direction and at 20mm from the cylinder
top surface.