Back to technical page
Ignition Coil Rewind
by Bob Board

I bought a Kanguro, in good condition but hard to start. I found the ignition coil to measure about 150 Ohms so decided a rewind was needed. (Please note any measurement below 160~170 Ohm of the ignition coil will result in difficult starting - webmaster).
  1. Remove the flywheel with the correct puller (M27 x 1,25).
  2. Disconnect and remove the stator. If removing the coil assembly from the stator backplate, drill off the heads of the rivets / clevis pins from the rear of the backplate, this enables the backplate to be pulled away without having to drive the rivets through (so there's then no chance of cracking the backplate).
  3. Remove the rivets from the core laminations by carefully punching them through. You may be able to remove the coil from the assembly without going through the above, which would cut out some work.
  4. Gently prise up the folded over laminations that hold the coils in place - I used a penknife blade to raise them, then large flat-nose pliers to flatten them. (On my assembly the ign coil is held by two folded above the copper voltage limiter, the coils either side of the ign coil are only held by one).
  5. Scrape away the varnish at the joint areas and persuade the coils to lift enough to remove the ign coil (having first cut or desoldered the earth connection).
  6. Inspect the old coil, on mine the former was very fragile, so that my first attempt at rewinding ended up by cracking the former.

the original ignition coil on the alternator with the yellow tape around it

I used 0.15mm enamelled copper wire from wires.co.uk. I bought a 500g coil, but that is way too much, 50g is probably enough. They also do the wire with a solderable enamel, which would make it easier to connect. To wind the coil, I used an old hand-cranked grindstone, by taking off the stone I could mount the former onto the spindle, then I had a 10:1 gear up for winding. I also made a simple mount for the coil of copper, so I could suspend it above the winder.

the new bobbin (coil) from a 50cc moped

the alternator taken apart

the new 0.15mm wire
which I used for the rewind

the sizes of the empty coil:
  • overall "outside" size: 34x30mm
  • overall "height" size: 15mm
  • outside size of the "hole": 20x15mm
  • inside size of the "hole": 18x13mm
  • material is 1.5mm thick

the grinder with the 1:10 gear


I soldered one end of the copper wire to some multi-strand instrument wire, reinforced the joint with some heat shrink insulation, then used PTFE tape to hold it in the former.

Now the hard bit – make yourself comfortable in front of the winder and tell everyone to leave you alone! Start winding slowly, counting turns, keeping tension on the copper and trying to ensure an even spread of winding across the former. You should be aiming for 3000 turns / 300 Ohms. I found that the coil was full at about 2800 turns so I terminated the end in a similar way to the start, wound some tape round to hold and measured the resistance at about 250 Ohms, you may consider using 0.125mm wire instead.

Advice: use 0.125mm wire

Next a good dipping in varnish, leave it to dry and remount on the stator. I found that the coil was slightly bigger than original, so is a tight fit between the two adjacent coils. All three now sit a little further out than originally. Replace the copper voltage limiting device (if fitted originally) and reconnect the earth connection and green wire to the ignition.

I then used nuts and screws to reattach the coils to the core. Refit the stator unit, flywheel back on (ensuring nothing fouls on the new winding), reconnect, switch on, 2 kicks and yahoo!

I then checked all connections, nuts, bolts, etc. Replaced the side cover and went for a short ride – great. 300km's later, still no problems, starts easily. Thanks to Tony Kersbergen for supplying the coil former – I’m still looking for a source of formers or complete coils.

Requirements:
  • Solderable enamel copper wire (0.15mm or 0.125mm);
  • Coil former;
  • Multi core wire (instrument wire);
  • 2mm heat shrink tube;
  • Insulating tape;
  • Varnish.


Back to technical page
Back to index page