auto plug magneto covers

An informal TYC survey suggests that as few as 1 in 8 Yaks still use Russian plugs and the factory ignition harness.

At some point it's a foregone conclusion that the insulation on one or more of those eighteen tightly bundled plug leads will break down, inside that curved metal Factory shroud, and start sharing its life story with a neighboring wire. There may be radio noise, engine misfiring at high power settings or other mayhem.

But when the time does come to switch to Auto plugs, be sure of this:

First, nobody makes the switch until they have to. Russian plugs work great even though they are more costly than the NGK’s you will fit next. 

Second, nobody fixes failing Russian Ignition harnesses. Not even DOSAAF mechanics did. Too time consuming and ambiguous to troubleshoot- they would toss it & fit a new harness.

Today, thanks to Modern Auto plug wire technology, you have another option.

Third, once you get to actually installing these Automotive Ignition leads on your Yak, you’ll experience a whole new level of frustration while trying to make a sound connection between the Distributor cap and the new conductor core.

The Russian plug wire is the most basic stranded conductor imaginable. Once the pointed metal screw  in the ​red mica Magneto distributor cap pierces the black rubber insulation, a metal to metal contact is assured. Screw that baby home & go flying.

By contrast, Auto plug wire yields to external penetration in a more nuanced way. 

After one half-turn of the pointed screw, your continuity meter will be beeping, (usually indicating 4 to 7 ohms between its ends depending on the plug wire length) ...but turn the screw in another half turn and continuity is suddenly lost!

Here's why. The core resembles a hollow Nylon guitar string. Around this flexible base a ceramic spiral conductor is laid. Someone determined the physics of this spiral transfers High Tension better than the Russian stranded stuff. It's efficient, but fragile - easy to break with a pointed screw. (Outside the spiral will be a thick layer of fibrous insulation then the colored plastic outer sheath, perhaps with an extra layer of RF shielding braid.)

One recipe for installation success is to strip the outer layers for quarter of an inch - being careful not to cut the guitar string or the spiral conductor. Once this delicate ceramic layer is visible, take the barrel of a crimp style automotive connector- trimmed to match the stripped length - and, using suitable pliers, close it firmly around the carbon spiral. Now the tip of the pointed screw will sink into the soft aluminum of the crimp, making a more reliable contact.

Simply ( As they say in the instruction manuals) repeat 17 more times, checking continuity & noting end-to-end resistance as you go.

Since you’ll have purchased Auto plug wires with molded-on plug caps, remember to thread ignition leads through their respective holes in the Magneto cover plate before terminating them at the Distributor cap.

The cap for the left mag has 10 holes (because of the Shower of sparks lead), the one with 9 holes is destined for the right Magneto.
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4 fixing Screws per Magneto cover, drilled for safety wire, are included in the kit.

These covers are drilled for 6mm diameter Auto Ignition Leads but can be enlarged to suit larger diameter plug wires. Note the middle lower pair of Ignition Lead holes are splayed outward on purpose to guide those two conductors towards their corresponding receptors on the distributor cap.