since 1940

Lycoming or Continental aircraft engine binds when hot

Engine is stiff or hard to turn propeller when hot. Maybe not every time.

1. Piston pin is protruding out of the piston and pressed against cylinder wall and binding in piston pin boss. 

2. Loss of main bearing clearance. One method in which main bearing can be lost is when the crankcase is not torqued tight and the crankcase surfaces fret (rub) against one another. This causes a looseness in the bearings and the thru-studs. Later if the thru-studs are re-torqued this pinches the cases together thereby taking up bearing clearance Ground aircraft and do not fly until engine is repaired. 

There have been several service bulletins issued by Continental and Lycoming on this subject. For example, Continental SB M87-26, subject: Piston Pin Replacement and Thru Bolt Torque Check applicable to the TSIO520CE calls for a check for engine stiffness by attaching a scale 30 inches station on the propeller and measuring the rotational force. In this case 20 to 30 pounds.

Another Continental Service Bulletin M89-14 for the TSIO-520BE subject: Thru Bolt Torque Check and Visual Inspection #2 Main Bearings  has as one of the inspection items a Crankshaft End Play inspection by rotating the propeller (with magnetos properly grounded) at eight different positions for example. This bulletin has much additional information on checking end play and propeller torque and makes interesting reading.

Recommend you check for any applicable Service Bulletins and check with the manufacturer to determine what the rotational force should be for your engine.

3. Chrome piston rings in chrome cylinder barrel. This causes severe scuffing of the cylinder barrel and is usually associated with scraping noises when engine turned by hand and metal flakes in oil screen. Might also be associated with paint burning on the cylinder barrel.

Lycoming connecting rod bearing. Notice material missing in center of bearing.

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