Piston Pin Inspection; Piston Clearance - Polaris 1999 Sportsman 400 Service Manual

ENGINE TOP END
§
t
127
c. Subtract the outer diameter of the piston pin
from the ins ide diameter of the piston pin
bore . Thi s will dete rmine the pisto n
pin-to- pisto n clearance.
d. Refer to the spec ification listed in Table 4. If
clearan ce exceeds the specificatio n in Ta ble
4. replace any worn part(s).
9. Measure piston-to-cylinder clearance as de- ...._ .....
scribed under Pis /oil Clea rance in this chapter.
10. If damage or wea r ind icate piston repl acem en t. . ._ _
select a new piston as described under Piston Clea r-
alice
in this chapter. If the piston . rings and cy linder
arc not damaged and are dimensionally correct,
they can be reused.
Piston Pin Inspection
I.
C lean the piston pin in solvent and dry thor-
oughly.
2. Inspect the piston pin for chro me flaki ng or
cracks. Replace if necessary.
3. Oil the piston pin and install it in the connecting
rod. Slow ly rotat e the piston pin and chec k for ra-
dial play (Figu re 133).
4. Oil the piston pin and install it ill the piston. Check
the piston pin for excessive play (Figure 134).
5. Replace the piston pin andlor piston or connect-
ing rod
if
necessary.
Piston C lea r a nce
I. Make sure both the piston skirt and cy linder wall
arc clean and dry.
2. Measure the cy linder bore diameter and check
for ex cessive taper and out-o f-round using a bore
gauge. inside micrometer or telescopi ng gauge
(Fjgure 135). To determine if the cy linder is exces-
sively tap ered. take three measurement s:
a. 12.7 mm (0.50 in.) dow n from the top of the
cy linde r block.
b. At the center of the cylinder bore.
c. 12 .7 mm (0.5 0 in.) up from the bottom of the
cy linder block .
3. To
determin e if the
cy linder is o ut-o f-round,
per-
form
the measurements aligned with the piston pin,
then at 90·
10
the piston pin.
4. If the cylinder bore diamete r is excessive ly
worn, tapered or o ut-of-round. bore the cyli nder to
the next oversize and replace the piston and rings.