DATE RELEASED: February 19, 2021 TITLE: YO-233-B2A Maintenance Manual DOCUMENT PART NUMBER: MM-YO-233 (Supersedes Maintenance Manual LM-YO-233, dated June 2012)

SERVICE LETTER NO. L283 Alternate Ignition System DATE: February 19, 2021 TO: All Owners and Operators of Lycoming YO-233 Series engines REASON FOR PUBLICATION: This Service Letter is announcing the availability of an alternate ignition system to replace the Champion Aerospace Electronic Ignition System (Lycoming P/N 66K26674-Y) on YO-233 Series engines. Installing this alternate ignition system...

SERVICE LETTER NO. L284 Blemish on Cylinder Barrel DATE: March 17, 2021 TO: All Owners and Operators of Lycoming O-235 Series engines REASON FOR PUBLICATION: This Service Letter is in response to reports of a blemish in the black oxide coating of P/N 16A26616 Cylinder Assemblies.

SERVICE INSTRUCTION NO. 1569 B DATE: April 21, 2020 SUBJECT: Installation, Operation, and Maintenance of Lycoming Electronic Ignition System (EIS) MODELS AFFECTED: Lycoming 4 and 6-Cylinder piston aircraft engines TIME OF COMPLIANCE: At the owner/operator’s discretion. REASON FOR REVISION: Revised the SUBJECT line. Formatted pages 4 through 18 to indicate separation between Installation, Operation...

Service Bulletin No. 642A Incorrect Piston and Ring Combination June 16, 2021 MODELS AFFECTED O-235-C, E & H series, and Factory Cylinder Kit P/N 05K23039 TIME OF COMPLIANCE Within the next 10 hours of operation or next scheduled maintenance event, whichever occurs first. REASON FOR REVISION: Deleted NOTICE “Only cylinders that …”. Added CAUTION and instructions for cylinder replacement before the...

SERVICE INSTRUCTION NO. 1280 D DATE: July 20, 2021 SUBJECT: Rotator Type Intake Valves MODELS AFFECTED: All Lycoming engines built with the conventional, large head intake valve No. 73117 including: IO-360-A, -C, -D; AIO-360-A, -B; HIO-360-A, -C; LIO-360, TIO-360-A, IO-720-A, -B, -C; VO, IVO, TVO, TIVO-540; IGO, IGSO-540, IO-540-A,B,E,G,K,L,M,P,S; TIO-540-A,F,J,N and LTIO-540-F,J,N. Engines...

SERVICE LETTER NO. L287 Increased Fuel Economy and Improved Manifold Pressure Stability DATE POSTED: August 17, 2021 TO: Owners and Operators of Lycoming TEO-540-C1A REASON FOR PUBLICATION: Announcement to TEO-540-C1A operators for the availability of the new ECU calibration and components to increase the fuel economy and improve the manifold pressure stability.

SERVICE INSTRUCTION NUMBER 1037 Y SUBJECT Approved Pistons, Rings, Cylinders, and Gasket Set Application for Use on Lycoming Aircraft Engines DATE August 25, 2021 MODELS AFFECTED All Lycoming opposed series aircraft engines in Table 1 TIME OF COMPLIANCE When installing new rings, pistons, valves, and cylinders REASON FOR REVISION Removed Table 1 – Alternate Piston Ring P/Ns. Changed all table...

SERVICE LETTER NO. L285 Change in cylinder configuration for O-235-C, -E, and -H Series engines DATE: August 25, 2021 TO: All Owners and Operators of Lycoming O-235-C, -E, and -H Series engines REASON FOR PUBLICATION: Lycoming supplied cylinders for O-235-C, -E, and -H Series engines were previously plain steel, straight-bore cylinders. This design has been replaced with nitrided, choke-bore...