Tech Tip: Measuring Flange to Flywheel

In this Tech Tip, we’ll review how starter spacers are utilized as well as how to measure the starter flange to flywheel so that during any maintenance, the starter is properly mounted and performs as designed.
The starting motor is an intermittent use component used exclusively to crank the engine via the flywheel at a sufficient speed to start the engine.
The starting motor at rest must be disengaged and properly positioned far enough from the flywheel so that it does not create interference when the engine is running, and close enough to properly engage when an engine crank is desired. This distance from the starting motor flange mounting surface to the engine flywheel is referred to as the flange-to-flywheel dimension, and is a standard set by engine manufacturers.
In most cases, the transmission or flywheel housing where the starting motor mounts is designed and machined with the specified flange-to-flywheel dimension with no additional components or spacers needed.
In some applications, the housing may require the use of an OE-provided spacer that comes with the engine.  It is designed to ensure proper clearance between the starter pinion and the engine ring gear.
During removal of the starter, it’s not uncommon for the OE spacer to stick to the old starter. It’s always good practice to check if the spacer is attached to the old starter nose housing during removal. It may also be attached to the engine. Secure it for re-installation.
If you are unsure if the engine requires an OE spacer—or if it’s damaged or lost—we recommend you contact the engine manufacturer for details, or measure the flange-to-flywheel dimension.
The flange-to-flywheel dimension on the engine specified by SAE is typically 49.3 to 52.3 mm, from the starting motor mounting surface to the ring gear face.
In order to measure this dimension, you must remove the starter. Make sure the mounting surface is clean and free of debris. Using a depth micrometer, place it flat on the mounting surface of the flywheel housing and measure the distance to the ring gear face.
If you have any questions, contact Technical Customer Service at 800.372.0222 or visit our product portfolio online.

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