Starter motor follies

[Dave Nadler]

Once upon a time, long ago and far away, Solo selected the NipponDenso starter motor part number 128000-1671 12v, and it worked AOK. Then, NipponDenso changed manufacturing to Taiwan and (at the same time?) changed to an Oilite (oil-impregnated sintered bronze) front bushing. Oilite works great for most applications, however... Later on, NipponDenso stopped making the starter. Only known manufacturer at this time is World Power Systems (Chinese parent company, producing in Taiwan), WPS part number 17383N, also with Oilite front bushing.

The Solo vibrates a lot. When the engine is running, this vibration damages the starter motor. How? Well, the starter motor core weighs 2kg, and the Bendix drive and pinion gear are way in front of the front bushing. Think of a weight at the end of a lever. With a small amount of play in the bushings, the motor core moves back and forth, hammering the bushing. The bushing is soft, so it yields, increasing the play, which increases the hammering force. Thus for some hours of operation no problems, but the play is gradually increasing. When it reaches 1mm it then increases really rapidly. The hammering also pits the motor shaft, which means actuating the starter grinds things up more.

Solo now buys the WPS starters and replaces both front and rear bushings with a filled-plastic bushing from the German company IGUS. This material seems to last (Solo tried several materials). So newer ArcusM shouldn't have the problem. Unfortunately the bushing material change was made without Solo's knowledge so its not possible to tell which gliders will have this problem. Also, there are no manufacturer markings on any version of these starters (the two I have here do say "Made in Taiwan").

Here's what my starter motor looked like inside - quite a pile of bronze shavings in here (front housing/bushing at bottom of picture)

SH recommends replacing the starter at 3mm end-play. My starter reached 3-4mm end-play at 12 hours of engine run time. I purchased a WPS 17383N starter (available from online vendors) and a replacement front bushing/housing assembly from Solo. Disassembled WPS starter and replaced front assembly. I also rebuilt my original starter for a spare (polished the motor shaft and replaced front bushing).

Thanks to Wolfgang at Solo for explaining this to me and helping with repairs including rapid parts shipment! Thanks also to Bernd at SH for tips on replacing starter (I'll polish this up and publish a link shortly).

In Summary:
- Check your starter motor end-play during pre-flight inspection, should be 3mm or less.
- If you need to replace your starter, get a complete starter from Solo, or
- If you use a WPS starter get a new the front housing/bushing assembly from Solo (otherwise you'll replace again in 12 hours).
- The problem is neither bushing quality nor lubrication...

May the EMF be with you!
Best Regards, Dave