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Replacing the secondary ignition wire

by Had Robinson

This repair replaces the secondary wire used in the Italian IDM ignition coils with a premium quality wire that will last many times longer.  This fix uses the same method of fastening the wire as IDM at their factory.  The failure of the secondary wire makes it harder to start the engine and causes power fade at the high end.  It should take less than an hour to complete compared to about three hours to replace the coil, to say nothing of the additional and unnecessary expense.  Remember that it is very rare for the coil to fail.

The repair works for any Italian made paramotor.  If you install the kit on other paramotors be sure that the OEM wire is 14" or less in length.  If it is longer, contact us for a custom kit that will fit your paramotor.

WARNING: Do not purchase this kit if the coil is faulty.  Any digital multimeter can be used to check the condition of the coil. Stick a sharp pin or needle into the secondary wire about 3" from the coil and measure the resistance from the pin or needle to the engine ground e.g. one of the aluminum cooling fins on the cylinder.  It should be about 10K Ohms (the resistance of a good coil plus the resistance of 3" of secondary wire on a Top 80 – other engines may vary).  If you do not see any resistance at first, withdraw the needle and stick it in again closer to the coil.  If it is less than 10% of 10K Ohms (or open/infinite) in a Top 80 coil, the entire coil assembly must be replaced.

Special tools needed

Parts needed

Secondary wire replacement kit is available from Miniplane-USA.  It includes:

top 80 secondary wire repair 

No matter what wire or type of spark plug is used, VHF AM aviation band radios will NOT work near a paramotor unless the ignition system is completely and tightly shielded.  Thankfully, the common 2 meter FM band radios are not affected as much by ignition noise.

Read through this section completely before beginning the actual repair.  Take a look at this video for some tips on the process.  The video only shows the major steps.

1. Remove the holding clamps from the old secondary wire – The clamp on the cooling air duct is held with a plastic screw.  When replacing the clamp later, it is best to use a small metal screw for reattaching the clamp rather than the OEM plastic screw.  You will need a drill and a 1/8" bit to remove the rivet that attaches the second clamp to the cooling box.  Drill the head of the rivet just enough so that the head pops off.  Remove the clamp and push the rest of the rivet through the cooling box with a nail.  Find a small bolt and nut to reattach the clamp later.  Be sure to use threadlock on the bolt and nut or it will loosen!

2. Remove the old wire from the coil – Using a razor blade, slice the existing piece of heat shrinkable tubing (HST) lengthwise where it surrounds the old wire at coil.  Peel off the old HST.  Using the hot air gun at the low setting, heat up the area where the wire enters the coil (see the 1st segment of the video).  As you heat the area, gently pull on the wire.  It should take about (60) seconds for things to get hot enough for the old glue to melt and the old wire to be pulled out.

Do not get things too hot!  If there is any smoke coming from the area, back off the gun from the area but continue to pull gently on the wire.  If things get too hot, the high tension terminal housing and its internal connections could be damaged!

3. Check the resistance of the coil again  If it is not 8.5K Ohms ±10%, you will have to replace the coil.  A low value means that the coil has internal shorts and will not perform well.  DO NOT CONTINUE WITH THIS REPAIR UNLESS YOU ARE CERTAIN THAT THE COIL IS OK!

Top 80 ignition coil being tested

4. Check the clearance between the high tension terminal on the coil and the cooling box.  It may be very close, almost touching the post.  You may have to take a fine saw or a Dremel tool to remove some of the aluminum metal of the box so that the new shrink wrap will fit over the post.  Be careful NOT to damage the plastic terminal.  The tight fit of these items are not good in any case because they rub against each other, loosening things up.

Top 80 ignition coil clearance

5.  Temporarily secure the boot end of the new wire to the top of the engine near the spark plug hole with a piece of masking tape.  This must be done so that there will not be any tugging on the end of the new wire while you are attaching it to the coil.  (If you attach the new wire to the spark plug you will just have to remove it again when you test the resistance of the new secondary wire before curing the HST.)  There is also a significant chance you will yank things if the boot is attached to the spark plug.

6. Install the large piece of HST  Slide the large piece of HST onto the new wire.

top 80 secondary wire repair

7. Install the small piece of HST  Slide the small piece of HST (white arrow) over the exposed core at the end of the new wire.  The photos below are with the coil off the engine for the sake of clarity.

top 80 secondary wire repair

8. Install the new wire  Gently push the wire into the high tension socket on the coil so that the barbed steel post slips inside the small piece of HST and solidly touches the core of the wire.  You will know you have done it correctly if you can gently pull on the wire and it does not pull out.  The wire must be completely inserted into the socket and none of the core should be showing.

top 80 secondary wire repair

9. Test the resistance of the new wire  You MUST check the resistance of the new wire assembly before you make the joint permanent to be certain that the new wire and the coil are electrically connected together.  With the digital multimeter, measure the resistance of the wire from the spark plug terminal inside the boot to a cooling fin on the engine.  The resistance should be 8.8K Ohms ±10% for the Top 80.  Other engines may have a slightly different value.

10. Slide the big piece of HST over the high tension terminal on the coil.

top 80 secondary wire repair

11. Apply low heat with the gun, moving the gun back and forth over the HST.

As you apply heat, you will see the HST start to shrink around the terminal and the wire.  Because the adhesive is slippery when hot, the HST will tend to slide off the socket as it shrinks.  You must use a small stick or pencil to hold the HST in place while it is being cured.

Keep applying heat until you see the adhesive ooze out of the ends of the HST.  When this happens, STOP APPLYING HEAT IMMEDIATELY.  Continue to hold the HST in place for at least one minute after heat is removed.  If the HST has moved off the socket a bit, you can push it back on and hold it.

Do NOT move ANYTHING until everything cools down completely.  It can take a full minute or more.

The adhesive in the HST will firmly grab the new wire and hold it on to the high tension terminal as well as seal the connection from water, oil, and dirt.  If you make a mistake, we can send you a new piece of the special HST for $5 shipping included.

Below is a photo of the how the completed connection should look like.

top 80 secondary wire repair

12. Check the resistance of the new wire to ground.  It should be around 10K Ohms for the Top 80.  Other engines may have a different value.

checking the resistance of the secondary wire and coil

13. Reattach the secondary wire to the engine cowling and the cooling box using the clamps.  THIS MUST BE DONE or the new wire may be destroyed by the intense vibrations of the engine.

14. Attach the boot to the spark plug.  Apply "Spark Guard" or equivalent to the inside of the boot with a toothpick.  The boot should be gently twisted and pushed down over the plug.  The boot is correctly seated when the gap between the bottom of the boot and metal base of the plug is about 1/8" (4mm).  If the boot is not correctly attached, the engine vibration will destroy the internals of the new spark plug boot.

The completed installation.  If you accidently damage the spark plug boot, we have replacements.  Please contact us to order.  Suggestions that will improve this repair are welcome.  Other pilots will benefit.  Always fly safely and responsibly.  – Had

the new secondary wire installed on the Top 80