Rotax 912 i Series Maintenance Manual page 215

INSPECTION
DISPLACEMENT PARTS - INSPECTION
Preparation
- Clean all parts carefully. See also section 05-
00-00 Procedures
PISTON - INSPECTION
Step
1 Remove the piston rings with the piston
ring pliers.
NOTE: Removed rings must be re-ins-
talled in the same position and
location.
2 Remove carbon residues from piston
rings and ring grooves and from the piston
crown.
NOTE: The best way to clean the
groove root is with an old, bro-
ken piston ring.
Multiple deposits are likely if AV-
GAS 100LL is used.
3 Check the groove for the piston pin circlip.
Carefully remove any burrs.
NOTE: If the groove is excessively worn
(>0.3 mm (0.0118 in.) than the
retaining ring), the piston must
be replaced.
Fig. 5
1. Piston rings
3. Piston crown
Effectivity: 912 i Series
Edition 1/Rev. 0
BRP-Powertrain
MAINTENANCE MANUAL
Procedure
2. Ring grooves
4. Piston pin circlip groove
Two sizes of pistons are available, red
NOTE:
and green. The difference is 0.01 mm
(0.00039 in.). The "red" piston is the
smaller one. The nominal size of the pis-
ton is stamped on the piston crown.
Oversized pistons are not available. The
piston is only delivered with 3 rings.
Step
4 Visually inspect and measure the piston.
Measure the cylinder and determine the
permissible installation clearance. See
also section 72-30-10 Wear limits.
NOTE: If the determined installation
clearance is greater than the
permissible installation clea-
rance, the piston and/or cylinder
must be replaced.
5 Determine the diameter of the piston pin
bore. See also section 72-30-10 Wear li-
mits.
The flank clearance can be measured on
NOTE:
the installed rings using a feeler gauge.
Multiple deposits in the spiral expander
of the oil scraper ring suggests that AV-
GAS 100LL has been used.
Fig. 6
1. Pistons
3. Feeler gauge
Procedure
2. Ring grooves
72-30-10
Page 7
July 01/2012