Honda BF135A Manual page 361

CHAIN CASE DISASSEMBLY:
1) Check the 43 x 58 x 7 mm oil seal for cut and other damage and replace if necessary.
Remove the 43 x 58 x 7 mm oil seal using a commercially available oil seal remover.
Replace the 43 x 58 x 7 mm oil seal with a new one on assembly.
2) Remove the CKP sensor and the chain case cover from the chain case.
Replace the CKP sensor at the 15 x 1.9 mm O-ring with a new one on assembly.
[1] CHAIN CASE
[5] CKP SENSOR
6 x 16
9-7
6 x 14 (3)
[4] 15 x 1.9 mm O-RING
[2]
CHAIN CASE COVER
[3]
43 x 58 x 7 mm
OIL SEAL