Engine Assembly; Crankcase Preparation - Upper; Piston Ring Installation - Polaris 2009 Sportsman XP 850 Service Manual

ENGINE ASSEMBLY

Crankcase Preparation - Upper

1. Refer to Oil Flow Diagram (page 5.4) and trace the oil
path through the upper crankcase / cylinder. Flush all oil
passages with solvent and then warm soapy water. Rinse
with clear, warm water and dry with compressed air. Be
sure passages are clean and dry before assembling the
upper crankcase.

Piston Ring Installation

Apply clean engine oil to rings. Check installed gap before
installing on piston. Clean accumulated carbon from ring
grooves and oil ring lube holes if piston has been in service.
1. Place oil control ring expander in oil ring groove. Tips of
expander gap (A) must face piston crown so scraper edge
(B) of expander faces piston skirt.
2. Rotate expander in groove until butt ends are on intake
side of piston. Ends must butt squarely together and must
not overlap.
3. Install bottom rail first, then top rail with end gap located
as shown at right.
Oil Control Ring Installation
Top Rail
Expander
A
4. Install second ring with undercut facing bottom of piston.
Rotate ring to place end gap generally toward (intake) side
of piston as shown below.
5. Install top ring with "0" mark facing up (toward piston
crown) and rotate to position the gap generally at the front
as shown below.
6. Be sure top and second rings rotate freely in their grooves
and do not bind when compressed by hand.
Bottom Rail
B
Oil ring expander butt end
2nd ring gap
Intake
PTO
Exhaust
Oil ring rail
Top ring gap
"0" mark on top
Barrel face
Undercut facing down
(piston skirt)
Notched face
ENGINE
MAG
5
Oil ring rail
5.51