Preparation
Carefully remove the hood of the engine to expose the engine and its parts. Use a can of compressed air, the product that is normally used to clean computer keyboards, to spray the engine, removing excess dirt and fuzz. Spray from a distance of about 6 to 9 inches to avoid damaging any parts.
Products
When you have finished spraying the engine of excess debris, use a mild liquid dish detergent to remove dirt and grime from the engine. Avoid using a harsh, abrasive cleanser, as it could result in residue buildup and damage the fragile engine parts.
Cleaning Tools
Tools to help you clean your old Lionel train engines can be purchased through an authorized dealer, or you can use more basic items available from any retail store. A shaving brush or toothbrush with soft bristles is a good tool to use to apply the detergent. When cleaning the engine, use soft and even strokes in applying the detergent to ensure a complete cleaning. Strokes that are heavy and forceful could damage the parts. Use a soft cotton cloth to dry the parts after you finished cleaning.
Finishing Up
Once you have cleaned and inspected the engine, allow the parts to air-dry before re-attaching the engine hood. Make sure all parts are tightened before operating the engine.