No-Spark Mystery

[Dr. Frankenstein]

I swear, this 'No Spark' category ought to have it's own sticky....

I had my '64 CA77 running well a few weeks ago, I was just trying to get the idle dialed in and find out why it was bogging down when I rolled on the throttle; I had to set her aside for a few weeks to stop an oil leak from the shift-shaft(fixed), and then today went back out to start it again and get her dialed in - but now I have no spark!

I re-set the timing, cleaned the points, but still no spark. It cranks like a champ, but only in the #3 key position. Battery is charged at over 13 volts, fresh gas...but no spark.

I noticed when I was working on the bike before that the coil would get pretty warm, but it started readily. I kept the battery off the bike and on a Batterytender - I am mystified.

As an observation, I noticed that I have to jiggle the switch to get the headlight on, but it does come on, and the horn works...I'll go back out and look in the headlight bucket to see if anything is loose...but what else could it be? Bad coil? How could it go bad if it was just sitting there(Ha! Silly question!)? Again, another mystery to track down...

[Dr. Frankenstein]

Just checked the coil, and it was good; I have ohms continuity from the coil to the condenser and the points; the coils tested good; ohms through the plug leads; so why am I not getting 12 volts at the points? Bad points? They look good: I sanded the points to get a nice contact...gap is set at .356...


???

[DJM]

Gap is .356 but .356 millimeters, inches or something else.

If it's .356mm you are measuring in microns, very impressive.. You will only get 12 volts at the points when they are OPEN.

From memory there is a position on the C72series ignition switch when the starter motor will spin the motor but it won't start as there is no supply to the coil and other circuits, could be a wiring problem on the switch?

[Geoff Hastings]

Position 1 will spin the engine with no spark, as DJM says, you will only get 12v at the points when they are open. The black wire to the coil should also have 12v when the points are open. If not, then you need to look at the ignition switch, if you have 12v on the black but not the green then the coil is open circuit. As easy check to do is disconnect the two wires going to the coil,apply 12v direct the black wire on the coil with the green earthed to the supply battery, when you remove the 12 v you should get a spark, repeatedly touching and removing the 12v should produce multiple sparks. You could Try disconnecting the green wire at the points and see if 12 v is there, if so it could be fibre washers on the points cracked or wrongly fitted.

[Dr. Frankenstein]

Thanks guys, I'll try all that. I think sometimes I start seeing the forest for the trees.

(Yes, 'Scanning Electron Microscope' is my middle name...;)

As an afterthought, though, when I was cranking the bike over I didn't see any spark at the points, either. Even if if the timing was off, AND given that I was getting 12 volts at the points, wouldn't I at least see the points sparking...?


I hope it's not the switch - I'm beginning to get very - 'irritated' - with these Dream switches.

[Geoff Hastings]

There's an old engineering saying " when you hear the sound of hooves, think of horses not Zebras".

[Dr. Frankenstein]

Or alternatively, as the noted author Dr. Hunter Thompson wrote: "One hand washes the other - I fear no evil."


"What do you mean it's not working - press it again..."
- attributed to J. Robert Oppenhiemer, father of the atomic bomb.