[longdistancerider]

These tests are used to check the CDI system. There are no valid tests for the CDI unit so this is an elimination process. If all these tests are good then the CDI is at fault. Before replacing a CDI all these components have to test good.
Use a multi-meter and set it to measure electrical resistance in Ohms.

Coil Test:Primary Side.Measure the resistance between the Yellow and Green wires.
The Yellow and Green wires being measured will be coming out of the spark plug coil.
The resistance should be less than 1 Ohm. Spec is .35 to .55 ohms
Secondary Side: Measure the resistance of the spark plug wires with the plug end caps removed, they unscrew. Insert a probe into each wire. Spec is 7.2K ohms to 8.8K ohms for the stock Honda coil, other coils will have different spec's.
Plug End Caps: Measure the resistance of the plug end caps. Spec is 5K ohms. Replacement part number is NGK XD05F

Stator Tests:
The connectors used are found under the left side cover
Measure the resistance of the Pink and Green wires.
The Pink and Green wires to measure will be going into the bundle that goes along the frame and eventually to the stator. This is the advancer pickup sensor
The resistance should be about 135 Ohms. New Spec 129 Ohms

Measure the resistance between the White and Blue wires.
These wires to measure will be going along the frame and eventually to the stator also. This is the CDI power source
The resistance should be about 85 Ohms. New Spec 84.2 Ohms

Measure the resistance between the Brown and Light blue wires.
These wires to measure will be going along the frame and eventually to the stator also. This is the primary pickup coil, the aluminum piece outside the rotor
The resistance should be about 207 ohms. New Spec 203 Ohms

The stator ohm readings listed can exceed the old spec by no more than 1 ohm, more than that will have a negative effect on the timing advance.
The New Spec was obtained by measuring 2 NOS stators, fresh unused old stock early model with the bullet Blue and White wire connectors.

Run/Kill and Ignition switch Tests:
Connect one probe to the Black w/White tracer pigtail wire coming out of the main wiring harness that connects to the CDI unit. Connect the other probe to the negative battery terminal. The results should be:
Ignition switch on, Run/Kill switch in Run position: Infinite Ohms reading meaning an open circuit
Ignition switch on, Run/Kill switch in Off position: Zero ohms or close to that showing the circuit is closed/completed to ground
Ignition switch OFF, Run/Kill in any position: Zero ohms or close to that showing the circuit is closed/completed to ground

Alternator Tests: Select/connect to one Yellow wire with a probe. Connect the other probe to one of the remaining 2 Yellow wires, resistance should be below 1 ohm. Repeat twice using a different wire each time. If the readings are good then test each of the Yellow wires with one probe connected to ground. There should be an Infinite ohms reading meaning none of the charging coils is shorted to ground.

NOTE: Some VOM's are auto-ranging meaning they switch ohm scales as needed and some are range selectible. If you have to select the range be sure to do that matching the expected ohm range.
NOTE 2: Came across a different set of tests from Rex's Speed Shop in the UK

https://www.rexs-speedshop.com/wp-content/uploads/2018/10/Rexs-CB250400N-CB250400T-generator-testing-guide.pdf

 

[dtsmjr8dan]

This is what the group has needed for a while, Jim. It's been meted out in bits and pieces, but, having it all in one sticky is awesome.

 

[longdistancerider]

I've been meaning to do this for awhile, finally got around to it.

 

[turfnsurf4ever]

Hi Jim,

Brought my 84 CB450sc out of storage a few days ago. There is a 20 seconds delay between hitting the start button and starter starts cranking on the 1st try and around 10 seconds delay on subsequent starts. Tested the battery its fully charged and stator seems charging fine. Thanks...

 

[longdistancerider]

This could be the starter button or the solenoid. Put a test light to the Yellow w/Red wire are the solenoid, push the starter button and it should light up immediately. If not then the button switch is the source, if it does then either the solenoid is lazy or there's a ground problem for the solenoid

 

[turfnsurf4ever]

Thanks Jim, for the clear instructions. So its the solenoid and not the switch. A follow up quick question, the positive post on the solenoid is always live regardless if the bike ignition and kill switch are off. Is that normal?

 

[J-T]

Yes, the positive post on the solenoid is connected directly to the battery and should always be hot. The small yellow/red wire supplies power to energize the solenoid when the start button is pressed. When the start button energizes the solenoid it should "click" and you should then have power to the opposite large post on the solenoid. The cable on this post supplies power directly to the starter.

 

[longdistancerider]

If the solenoid is getting instant power from the Yellow w/Red wire when the starter button is pushed that's good. If the solenoid/starter is still delaying then find the Lt. Green w/Red wire coming from the solenoid and connect that directly to the negative battery terminal. If the solenoid/starter works immediately then the problem is in the neutral safety wiring or switches. If it still has a delay then the solenoid is bad.

 

[turfnsurf4ever]

Thanks JT. I didn't hear any click when I press the starter so the plunger must be sticking. I will order a replacement asap. In the mean time, can I hot wire the bike in a pinch by connecting the relay's 2 posts with a screw drive or an Allen key?

 

[longdistancerider]

Yes, you can jumper the 2 battery cable terminals to jump start it. Pliers seem to work easiest

 

[turfnsurf4ever]

HI Jim, IF the neutral safety switch is faulty, would the green neutral indicator light on the dash light up? Thank you.

 

[longdistancerider]

No, the light depends on ground thru the switch to work.
Grounds can work but have too much resistance. Use a VOM set to volts. Check battery voltage at the battery posts then move the negative probe to the engine block and a frame ground connection. The voltage should read the same minus maybe .1V. If the reading are within that then the grounds are good.

 

[SoapyCoyote]

I'm trying to test the spark plug wires with my ohm meter as per the sticky's instructions but I'm confused and would like some help, please. I was able to unscrew the plug end caps just fine, they tested bad at like 50k 0hms so I ordered new ones. Thanks for that part number! Found them on amazon for about $6 and change.

But now I am unable to remove the actual spark plug wires from the source (is this called the coil? It's a black cylinder under the gas tank on the right side or the "primary side" of the bike) to measure the resistance of the wires themselves. How do you actually perform this test? I tried inserting one probe into each wire as the sticky says to do and got nothing. Is this the right way to do this test, or should I continue to try to remove the spark plug wire and put one probe at each end of each wire treating the wires themselves as resistors?

Also, if this is how you measure the resistance of each wire, how do I remove the coil end of the wire from the coil? Thank you in advance! So grateful for this information and sticky!

 

[SoapyCoyote]

Also, here is a picture. I'm attempting to unplug my spark plug wires from here

 

[SoapyCoyote]

Ok, I'm a total noob... I used google and learned that yes indeed modern day spark plug wires do have resistance. But I still don't know the best way to disconnect these ones from my coil. Any advice?

 

[SoapyCoyote]

Are these spark plug wires the "non replaceable" type? I found this video on Youtube about how to replace non-replaceable spark plug wires. Any recommendations as to where to get the right kind of wire to use with the specified 7.2K ohms to 8.8K ohms of resistance?

Here's the URL to the video:

The guy uses a steel nail. I think I would want something more conductive like a brass nail or maybe copper.

 

[J-T]

The wires are permanently attached to the coil, not removable. If the coil/wires are bad you may want to consider the GM coil mod in another stickyl

You had the right idea, one lead on the ohmmeter connected to each spark plug wire. Should read 7.2 to 8.8 K ohms. When you say you "got nothing" do you mean zero resistance or infinite resistance? Do you have an auto ranging multimeter?

 

[SoapyCoyote]

Thanks for replying! Ok that makes sense. I'm sorry, I should have said I read infinite resistance. I tried poking the probes higher up, closer to the coil, and I still had infinite resistance on my ohm meter. It is auto ranging.

 

[J-T]

Cut the wires off until you can see fresh metal strands and re-check the resistance. If it still reads infinite you have an open circuit and a bad coil.

 

[SoapyCoyote]

Yeah it reads infinite resistance across the two spark plug wires no matter how short I cut the wires. So GM coil mod? I think I found the thread on that. Thanks!