OHK-0004 - Hartzell Engine Technologies Brush Assembly Overhaul Kit

OHK-0004 – Hartzell Engine Technologies Brush Assembly Overhaul Kit

Available now on the Airparts.aero Marketplace.

Overview

The Hartzell Engine Technologies OHK-0004 is an OEM-certified overhaul kit containing the essential components to rebuild the brush block assembly for specific Hartzell, Kelly Aerospace, and Prestolite-Leece-Neville aircraft starters. This kit is a critical element in the proper maintenance and overhaul of the starter motor's electrical system. The brushes are the primary components that conduct high amperage current from the starter's stationary housing to the segments of the rotating commutator on the armature, generating the powerful magnetic field that creates rotational torque.

This kit provides factory-new, dimensionally precise brushes and springs, which are essential for restoring the starter to its original performance and reliability specifications. Over time, the original carbon brushes wear down from friction and electrical arcing, and the springs can lose their specified tension. This leads to poor electrical contact, increased arcing, commutator damage, and eventual starter failure. Using the OHK-0004 kit during overhaul ensures that the heart of the starter's electrical circuit is restored, providing the reliability required for consistent engine starts.

Key Features

• OEM Certified Components: Contains genuine Hartzell parts, ensuring correct material composition, dimensions, and performance.

• Restores Electrical Performance: Replaces worn brushes and fatigued springs to re-establish optimal electrical conductivity and contact pressure.

• Prolongs Starter Life: A critical part of a starter overhaul that helps prevent costly commutator damage and extends the Time Between Overhauls (TBO).

• Precision-Engineered Brushes: The carbon-graphite brushes are specifically formulated for high-conductivity and controlled-wear characteristics in a high-current DC motor application.

• Specified Spring Tension: Includes new springs designed to provide the exact contact force required for proper commutation without causing excessive brush or commutator wear.

Technical Specifications

• Part Number: OHK-0004

• Component Type: Brush Assembly Overhaul Kit

• OEM Manufacturer: Hartzell Engine Technologies

• Kit Contents: Typically includes a set of carbon brushes and corresponding brush springs.

• Material (Brushes): Electrographitic carbon compound, engineered for high current density and lubricity.

• Material (Springs): High-tensile spring steel.

• Governing Specifications: Manufactured as part of a TSO or PMA-certified starter assembly, meeting all applicable FAA standards.

Aircraft Compatibility

This overhaul kit is designed for the brush assembly found in a wide range of starters used on reciprocating engines from Lycoming and Continental. Common starter models serviced by this kit include, but are not limited to:

• Hartzell/Kelly Aerospace Starters: ERZ-8011, ERZ-8021, SRZ-9011

• Prestolite/Leece-Neville Starters: MZ-4204, MZ-4222, MZE-4202R

These starters are factory installed or are STC'd for installation on a vast number of general aviation aircraft, including models from:

• Cessna, Piper, Beechcraft, Mooney, Cirrus, and many others.

Note: This kit is specific to the starter's brush block assembly. The starter's Component Maintenance Manual (CMM) or Overhaul Manual is the final authority for determining the applicability of this kit.

Applications

• Starter Overhaul & Repair: Used by certified repair stations and A&P mechanics to overhaul or repair the starter's brush block assembly.

• Preventive Maintenance: Replacing the brush assembly components as part of a scheduled starter overhaul or as dictated by condition.

• Restoration of Starting Torque: A key step in troubleshooting and fixing a slow-turning or weak starter motor.

Kit Includes the Following Items:

• 7505001 – 12 Volt Positive Brush Assembly (2ea)
• 7801001 – 5/16 Cadmium Split Lock Washer (1ea)
• 7801002 – 5/16 Cadmium Flat Washer (1ea)
• 7801003 – 5/16 Insulating Fiber Washer (2ea)
• 8101001- 5/16 Bronze Nut (1ea)
• L51-0009 – Round Green 12 Volt Label (1ea)

Why Choose OHK-0004?

The starter is a critical component for engine operation. Using a genuine Hartzell OHK-0004 kit ensures that the replacement brushes are made from the correct electrographitic compound, providing the required conductivity and wear resistance. Generic or uncertified brushes can be too hard, causing rapid commutator wear, or too soft, wearing down prematurely and filling the starter housing with conductive dust that can cause electrical shorts. The included springs guarantee the correct tension—too much tension accelerates wear, while too little causes destructive arcing. For a reliable, long-lasting starter overhaul, there is no substitute for this OEM-certified kit.

The engineering principle behind the OHK-0004 components is the management of the electro-mechanical interface between a stationary power source and a rotating armature. This process, known as commutation, relies on the brush's ability to conduct hundreds of amps of current across a microscopic, sliding contact point to a specific commutator segment. The electrographitic material of the brushes is specifically designed to create a thin, conductive film of graphite and copper oxide on the commutator's surface. This "patina" is critical; it reduces the coefficient of friction and, more importantly, lowers the electrical resistance across the gap, minimizing the voltage drop and destructive electrical arcing as the brush transitions from one segment to the next. The spring force is precisely calculated to maintain this delicate film without physically eroding the copper commutator bars, ensuring the efficient conversion of electrical energy into the mechanical torque required to start the engine.

Note: This overhaul kit is intended for installation by certified A&P mechanics or authorized repair stations during the overhaul and repair of aircraft starters. All work must be performed in strict accordance with the starter's Component Maintenance Manual (CMM) or official overhaul instructions. Proper seating of the brushes to the commutator is a critical step for ensuring optimal performance and service life.

Documentation

No public-facing OEM documentation was located for this specific kit part number. All authoritative data, installation procedures, and specifications are contained within the proprietary Hartzell Engine Technologies Component Maintenance or Overhaul Manuals for the specific starter models this kit services.