Motorstar NA: Radial Aircraft Engine Sales And Service

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SPC Pistons and Rings: Product Improvement Announcement


MotorstarNA is proud to announce that we now offer the SPC pistons and rings. The SPC piston kit uses a new piston design and modern technology rings.

The new pistons use a 3 ring configuration instead of the original 5 ring design.  The top compression ring is a plasma molybdenum ring that produces a superior seal while reducing friction.  The second ring is a tapered hook or Napier design that provides superior oil control. The oil ring is also modern design that reduces oil consumption by about 1/3.  The overall result is an engine that consumes less oil, more stable operating temperatures through all operating conditions. It runs smoother at idle and it starts more easily.

The factory engineer and test cell technicians were surprised at the test cell results. The engineer said of the testing, “After the breaking-in period we measured the parameters at all engine duties and the results were according to the documentation in force. After this we have set the engine at Cruise I and it worked at this duty for one hour. We did this test in order to determine the oil consumption. The result is amazing. The oil consumption at Cruise I is 510 grams per hour or 2.83 grams per HP (specific oil consumption) or 0.575 liters per hour (the density of our oil is 887 grams per liter”

Typically the M14-P consumes about 0.8 liter per hour.

He also said “Besides the oil consumption we observed also other improvements. The engine start is easy; the temperatures (CHT and oil temperature) are constant in time and the idle is more stable.”

            The SPC piston kits are available in standard bore size (105 mm) and R1 first oversize (.15 mm oversize). Each kit includes a new piston, 3 fitted rings, a new piston pin, two new piston pin plugs, a new cylinder base gasket, two rocker cover gaskets, two new rubber tube for the push rod tubes new cylinder nut lock tabs and installation instructions.

            The new piston is 34 grams lighter than the standard piston. The SPC kit includes a new piston pin plugs that are heavier to keep the engine in balance.

            The standard size kit P/N 14-605-22SPC is $304.00 per kit.

The oversize kit is P/N 14-605-22SPC-R1 is $328.00 per kit.

There wil be an additional 5% discount on orders of 9 kits.

            MotorstarNA will soon have these kits in stock at our Vermont headquarters.


Shower of Sparks Kit -- $385.00

 Shower of Sparks System Installed

5 Cylinder Conversion Kit For Slick Magnetos --$ 175.00

We now sell a conversion kit to make a slick 4 cylinder magneto into a 5 cylinder magneto. Our conversion kit for Slick magnetos contains the following items:

  • an aluminum cover;
  • a gear (from high pressure polyethylene);
  • a plug which holds the gear on the rotor shaft (from high pressure polyethylene);
  • a distributor cover (from textolite or hard plastic).
We used the distributor gear of the magneto because it has 40 teeth. For 5 cylinders the gear ratio between the magneto rotor and crankshaft has to be
1.25 (the magneto has 2.5 sparks per revolution). The gear ratio between distributor gear and the magneto rotor has to be 2.5. We did the gear of the rotor with 16 teeth (40/16=2.5).
For more information, email us at

Alternator Kit

 Alternator Kit

These adapters allow the installation of the Skytronics alternator on the M14 series engines. The complete kit includes the adapter shown and a 50 or 70 Amp alternator. The alternators come with a solid state regulator that includes overvoltage protection. We have also a Yak-52 install kit that will replace the Yak generator, regulator, overvoltage relay and the reverse current relay. They will save considerable weight as well as make it much more reliable.

Alternator Wiring Schematic

Please contact us at for details.