79 Jota Ignition

I

imtcaj

New member
Hi All,

My '79 Jota has got a non sparking single lead ND ignition coil. Before I rush out and buy another, can this be tested, or could there be another issue that could be causing this apparent coil failure.

Any thoughts would be greatly appreciated.

Many thanks and regards,

IMTCAJ
 
Hi, have you got a name, that's a bit of a Mouthfull  IMTCAJ

Swap the Low tension leads over with the other coil, make sure you put the plugs back in the caps and earth them against the motor and crank it over again.

You'll know then which direction you're headed, probably worth checking the ballast resistor against the other one too...

Rob
 
Hi Rob,

Many thanks, I've swapped all these leads over and tested again with no joy. So looks as though it's a new coil.

Regards,

Ian (IMTCAJ)
 
You can test the primary side of the coil easily enough. Just measure the resistance across the low voltage terminals. It should be around 3 to 5 Ohms. If it isn't, your coil is fucked.

If the primary resistance checks out OK, You can do the following basic function check of the secondary circuit.

Connect a spark plug, sit it on the engine where you can see it, connect a 12V supply to one of the coil's LV terminals (turning the ignition on should accomplish this). Then run a wire from earth (engine or frame) and briefly touch it on the coil's other LV terminal. You should see a spark at the plug when you interrupt the primary current (disconnect your earth wire from the coil). It probably won't be a strong spark because your makeshift "points" don't have a condenser across them, but you should still get a visible spark.

If you don't get a spark, check all connections including the secondary earth connection from the coil to the frame. If still no spark, try another coil.

Cheers,
Cam
 
Hi Cam,
Many thanks for the post. I?ve already done what you?ve mentioned above, and yes the coils do discharge when tested across an external battery. Interestingly enough, when hooked back into the bike?s wiring loom the single lead coil discharges when I stop cranking the engine via electric start. So an issue other than the coil.
Also, many thanks for the wiring diagram posted in late 2012.
Regards,
Ian
 
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