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How do I replace the shear pin on an NL series starter?

The NL and NL/ec family of starters uses a field-replaceable shear pin as part of the Kickback Protection System (KPS). If energizing the starter causes the motor to spin but the pinion gear does not rotate, the shear pin should be replaced. Follow the NL shear pin replacement instructions.

What causes the drive gear to break on a Sky-Tec starter?

Drive gear fractures are most commonly caused by engine kickback. Kickback can result from incorrect timing or fuel system problems. If kickback occurs regularly, diagnose and correct the underlying engine issue before replacing the starter drive, as the problem will likely recur. Many current Sky-Tec starters include kickback protection and are warranted against kickback-related damage.

What causes drive gear wear or ring gear damage?

This condition relates to improper starter drive extension or retraction and can affect all starter styles. If the drive gear does not fully extend during a start attempt, it is subjected to stress. If the drive does not disengage after start, the engine will continue to drive the gear, destroying the motor. In either case, rapid wear or fracture of the drive gear will result.

Does the starter drive require periodic lubrication?

Mechanical (Bendix) starter drives that are sticking should be cleaned with mineral spirits and lubricated only with silicone spray. Do not use oil or common greases, as they attract dust and grit and can cause the drive to stick or wear out prematurely.

Solenoid-actuated starters do not require cleaning or lubrication during normal use. If the starter is out of service for an extended period, the shaft can be lightly oiled to prevent corrosion.

Why does my starter engage intermittently?

There are two likely causes. If you have a mechanical (Bendix) drive starter, the drive may be dry and sticking. This type of drive should be lubricated every 50 hours of operation to maintain smooth engagement and disengagement.

The second likely cause is a faulty starter contactor. Contactors should be checked under load. Even a small amount of resistance in a 12V circuit drawing 60 amps can significantly reduce available current. A 0.2-ohm resistance, for example, can cause a 40 percent loss in starter operating power. To check the contactor, disconnect the lead from the starter, connect it to a battery load-meter tester, activate the contactor, and measure voltage on each side. A 0.1V drop is normal for a new contactor. A drop greater than 0.3V indicates the contactor should be replaced.

Why does my starter engage, but the engine will not turn over?

On Continental engines, the most likely cause is a slipping starter adapter. The starter adapter will need to be replaced or overhauled.

After releasing the start button, why does the starter briefly remain engaged?

This is normal behavior for a permanent-magnet starter. When power is removed, the permanent-magnet motor continues to generate power as it spins down, keeping the starter drive engaged for approximately half a second until RPM drops low enough for the drive to fully disengage.

Why does the starter drive remain engaged for an extended period after releasing the start button?

This is a potentially dangerous situation. Starter contactors in older aircraft can become welded shut after years of use. A welded contactor can cause the propeller to rotate any time the master switch is energized, regardless of the position of the start button or key. Replace the starter contactor immediately. The starter itself may have also been damaged and should be inspected for overhaul or replacement.

Why is my new lightweight starter noisier than my old starter?

Lightweight starters have less housing bulk surrounding the gear train, which provides less insulation from operating noise. Additionally, replacing a legacy heavyweight direct-drive starter with a lightweight model often involves switching to a gear-reduction drive design to achieve equivalent torque. Gear-reduction starters have a noticeably different noise signature than direct-drive starters. This is normal and not an indication of a problem.

How do I identify whether my Lycoming engine has a 122-tooth or 149-tooth ring gear?

The geometry between the teeth is the easiest way to tell the difference at a glance. A 122-tooth ring gear has a “V” shape between the teeth. A 149-tooth ring gear has a “U” shape between the teeth.

Lycoming Service Instruction 1141A provides additional detail on ring gear identification, replacement procedures, and a table of ring gear part numbers with compatible ring gear support assemblies.

Note that the ring gear actually installed on an aircraft may not match what the aircraft or engine was originally equipped with, as replacements may have been made over the years. Always confirm the actual ring gear tooth count before ordering a replacement starter.

Why doesn't the NL series starter work correctly with a Superior engine?

Superior reverse-engineered the 60882-type ring gear support assembly (designed for 122-tooth ring gears) when manufacturing their PMA-certified Ring Gear Support Assembly PN SL77579-1 Rev. 11, which is intended for 149-tooth ring gears. When this support assembly is paired with a 149-tooth ring gear, the ring gear sits farther aft than the Lycoming specification, creating a very small margin of interference with NL-type starters. Other starter models typically stand far enough back from the ring gear that the mismatch is less problematic, but because the NL starter is designed to meet Lycoming’s specified tolerances, it is sensitive to this dimensional variance.

When replacing a B&C or Kelly starter with a Sky-Tec, why does the alternator strap not fit properly? What hardware should be used?

Use a Lycoming alternator strap (Lycoming PN 74323) secured with MS20074-05-06 bolts (5/16-18 thread) to attach the alternator strap to the Sky-Tec starter’s alternator boss.