How do check for current to a coil on a 1978 honda cb400a?

Question

i have a 1978 Honda cb400a and i am not getting any spark to the plugs, how can i check to see if i got electrical current flowing to the coil?

Answer 1

Disconnect a spark plug wire, and pull the plug. Put the plug back on the the plastic spark plug cap, just like it was still mounted to the engine.  Then hold the plug very close to the head, being sure you are only touching the insulator. Put it in neutral. Now, crank the engine. if you progessively get the plug closer, you can be sure if it doesn't jump, from the plug to the head that the coil is bad.

If you are getting the out put from the coil, you can assume that it must be getting OUT of the coil.  (The negtive does not help you, though.)  

Are you a member of the yahoo group that supports the CB/CM-400A Hondamatic, and the odd 750A as well? You may find it helpful to read through the backlog of old messages.

I'd use a volt-ohm meter to decide if it was coil failure or if the CDI has packed it it in. The Old Bike Barn, I believe has coils that are good, for $70 bucks or so, and a non-factory Ignition unit $300.

Does a spark jump?  If so, you can write that side off.

Answer 2

Correct, test light or a multimeter. Check the wire from the ignition switch to the coil. Color code is anything but black. Being import I'd guess orange or yellow? With the switch on the light should light up or the meter should show 12 volts.

Answer 3

A test light you can use just a bulb and wire no biggie