My 72 A65 Thunderbolt has begun to run intermitantly. It is fitted with a boyer elctronic ignition. I can get it to start and the engine will run for a minute or two and then stops. There is no spark. I have checked the kill switch and all wiring connections and all appears OK. Is there a way to test the coils to see if they are serviceable?

cheers, Neil

New plugs ?

Do the coils feel hot ?
Be odd if both were failing together ?

Not knowing boyers coil requirements, they call for something special for some versions of boyer ? These 6v or 12v ? And do you have a resistance load in there as well ?

Could be a dud battery. Boyer is not voltage tolerant. If you have a multi-meter measure the battery as it is. It should be around 12 to 12.5 Volts. Then let the headlamp burn for about 2 minutes. Re-test the battery. If it has dropped below 11Volts its not holding a charge and the Boyer fails below 10 V.

Mick

Hi fellas, thanks for the replys. I have fitted new spark plugs which made no difference, the bike has plenty of fuel. The battery I have been using is about 12 months old, it is the one out of my Commando which also runs a Boyer system. My Commando runs fine with this battery so I am assuming it is ok?

I have checked the system this morning and there is no spark at all when kicking the bike over. If I ground the kill switch wire, this produces a spark at both plugs. I have been told that this could mean that the rotor/ stator unit is faulty or the coils are faulty or there is a problem with the black box. I was hoping to test the coils somehow to try to elminate them as being the problem

regards, Neil

Neil NICOLAO wrote:Hi fellas, thanks for the replys. I have fitted new spark plugs which made no difference, the bike has plenty of fuel. The battery I have been using is about 12 months old, it is the one out of my Commando which also runs a Boyer system. My Commando runs fine with this battery so I am assuming it is ok?

I have checked the system this morning and there is no spark at all when kicking the bike over. If I ground the kill switch wire, this produces a spark at both plugs. I have been told that this could mean that the rotor/ stator unit is faulty or the coils are faulty or there is a problem with the black box. I was hoping to test the coils somehow to try to elminate them as being the problem

regards, Neil

If you have a multimeter check the primary and secondary resistance of the coils, lots of info on the web on how to do it....and a multimeter would be good to have in any case for electrical troubleshooting, basic models are cheap these days

Coils can drive you to drinking.
Over 10 yrs old there all ' suspect ' .
Cycle Mag thought the 6 V ones were worse than suspect new , and Lucas 12V little Better .
There 2 bit K mart ones had about ten times the erg potential , or more .

Anything less than a 1/2 inch spark coloured Blue and White minimum = 1100 deg min ,
is a permanant missfire .

And if the Coils Are breaking down , When they feel like it . They WILL drive you to drinking.

When you break the primary you should witness spark across the electrodes of an exposed and properly connected and grounded known good spark plug.
That's all the points or boyer is doing, just timed to the compression.
Disconnect the boyer from the coil, run a jumper from the primary to the frame, run a jumper from the battery to the other coil primary and just bounce the jumper to the primary while watching the spark plug. Now there is nothing in the circuit other than the coil and the jumpers and the spark plug. A small spark as the jumper rubs the primary terminal should produce a spark at the plug.
Do all this in the absence of fuel leaks and vapours or there is risk of fire as in flames and destruction. If you're not comfortable don't do it.
If you are grounding the kill switch and seeing spark, as you stated earlier, the coil is working, I'd look elsewhere.