Topic: Still Need Coil Help

[campbmic]

Bike: 1975 CB 550

I'm reassembling my bike after painting the frame and I still can't get the coils firing right. I have tested the 2 Black/White wires, the blue wire, and the yellow wire all are constantly hot should this be the case?

My engine shutoff switch is totally destroyed so I ran a hot wire directly from the battery to the black/white wires when I had it running but now this doesnt seem to work.

Thanks for any help!

[TwoTired]

The coils draw power and store energy when the points close.  They fire spark plugs when the points open.
The points complete a path to ground (eventually the path to Battery Neg terminal).

If, as you rotate the crank, neither the blue nor the yellow ever reaches ground potential, the coils can't work.  Assuming the yellow and blue wires connect properly to the points, either your points are not mechanically closing or there is a film that is coating the points contacts which prevent the wires and coils connection from achieving the ground potential and completing a circuit.  Some films are transparent.  A points file is recommended to break through or wear off the film (not silica abrasives which will ultimately shorten point life).

The engine case needs a solid connection to the frame metal, not paint, which is an insulator for electrical current.  The battery NEG cable normally connects to engine and frame, on paint-free surfaces.  If these surfaces are insulated with paint, you will have quite a few electrical issues.

Also, if you have painted the engine where the points plate mounts, the paint can prevent electrical flow there as well.

In general, wherever you want current to flow, you must not only have power flowing to the device, but there must also be an effective return path back to the power source.

[campbmic]

Thanks for the help, I believe there is power getting to the coils. I took a voltmeter and found;

-Black/White wires connecting to the coils are both always hot
-Blue wire connecting to coil flickers on and off while turning bike over
-Yellow wire connecting to coil flickers on and off while turning bike over
-No spark from spark plugs =(

The coils are both warm to the touch so Im guessing they are getting energy right?

[OldSchool_IsCool]

Are you testing all 4 plugs?  What test method are you using?

If you have an ohm meter, test your plug caps.  They should read about 5000 ohms, maybe a few k more, when measuring between the spike and the plug clip.  Also check the end of the wire and the spike for corrosion.  If you see any green in there, clip off about a centimeter of wire to good copper and clean the spike. 

It would be hard to believe that all 4 failed at the same time, what with the bike running recently. 

[campbmic]

I'm testing all four and using a voltmeter with a testing light (it tests only whether or not a current is hot or cold). I am testing all four of the plugs this way and none of them work. If the coils are dead then won't they be cold instead of hot? Thanks!

Is there a way to take the coils of and ground them with a screwdriver or something and see if they fire?

[Spanner 1]

If the plugs are just sitting on a painted head they may not 'grounding'....also, are your points nice and shiny?

[pampadori]

I'm testing all four and using a voltmeter with a testing light (it tests only whether or not a current is hot or cold). I am testing all four of the plugs this way and none of them work. If the coils are dead then won't they be cold instead of hot? Thanks!

Is there a way to take the coils of and ground them with a screwdriver or something and see if they fire?

you're using a voltmeter on the ends of the spark plugs or wires?  can your voltmeter handle that many volts?

take a new spark plug, and attach it to each plug wire one at a time.  hold the plug against the cooling fins on the engine. Turn off all the lights in your garage.  attempt to start the motor.  did you see spark?

[TwoTired]

Tape or hold the two HT lead ends (no plug caps or anything) from one coil about 1/16 to 1/8 inch away from each other and spin the crank with power applied to the coils.  Each time the points open there should be a spark across the wire ends.  It doesn't matter if they are on the bike or not.

Tell us about the age/condition of your condensers.

Btw, you can't test each HT wire in isolation from the other, as they both function at the same time and require the other lead to complete the circuit path.