Service Instruction No. 1143 C

Counterweight Bushing Inspection, Replacement, and Special Tooling Upgrades

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Supersedes Service Instruction No. 1143B, Supplement No. 2, 3 and 4 to Service Instruction No. 1143B and Service Letter No. L217

November 10, 2011 

MODELS AFFECTED

All Lycoming piston aircraft engines with dynamic counterweights

TIME OF COMPLIANCE

During engine overhaul.

This Service Instruction includes all of the necessary information to examine, remove, prepare, and install  counterweight bushings. Because of counterweight manufacturing changes, some modifications to existing  tools used to replace counterweight bushings could be necessary. Instructions for tooling modifications also  are included in Appendix A of this Service Instruction.

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