• Don't overlook our Welcome Package, it contains many links to important and helpful information about functions at VHT like posting pictures and sending PMs (private messages), as well as finding the parts you need.

    AD

Ignition Diagnosis for CB/CM 400/450 Automatic Trans 1978-1983

Maraakate

Maraakate

Veteran Member
Joined
Jun 7, 2022
Total Posts
2,507
Total likes
639
Location
Lancaster, PA, USA
Original document by Jim O’Brien. Updated by Frank Sapone.

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, VOM or Volt-Ohm-Meter, with a new battery and set it to measure electrical resistance in Ohms.
Separate the three connectors from the stator to the CDI for the stator tests, use the stator side connections.
The fuel tank has to be removed to test the coil and run/kill switch. The Black w/White wire pigtail is at the CDI.

IF THE TESTS COME UP GOOD PLEASE POST A THREAD SO WE CAN VERIFY THAT YOU HAVE DONE THIS TEST CORRECTLY. WE DO NOT WANT YOU BUYING RANDOM PARTS IN A DESPERATE ATTEMPT TO FIX THE ISSUE AS IT CAN GET REAL EXPENSIVE, REAL QUICK!

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 0.35 to 0.55 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 specs.
• Plug End Caps: Measure the resistance of the plug end caps. Spec is 5K Ohms. Replacement part number is NGK XD05F.

⚠️IF THE PRIMARY OR SECONDARY IS OPEN THIS MEANS THE IGNITION COIL IS BAD, GET A USED ONE, DO THE GM COIL MOD, OR DYNATEK DC11-2 DO NOT BUY THE $20 EBAY COILS THEY ARE WRONG. ANY COIL OVER 1.0 OHM ON THE PRIMARY WILL CAUSE INCORRECT PILOT MIXTURE AND WILL CUT OUT SPARK AFTER 10 MINUTES OF RIDING. IF PLUG END CAPS READ INFINITY OR THEY ARE NOT CLOSE TO 5K OHMS THE CAPS ARE BAD, GET A NEW NGK XD05F CAP OR AFTERMARKET EQUIVALENT.⚠️

Stator Tests:
The connectors used are found under the left side cover.

• Measure the resistance of the Pink and Green wires in the large 6 pin connector. This is the advance pickup coil. The resistance should be between 10 to 30 Ohms.
• Measure the resistance of the White and Blue wires in the 2 pin connector. This is the power to the CDI. The resistance should be between 4 to 7 Ohms.
• Measure the resistance of the White wire in the 2 pin connector and Green wire in the large 6 pin connector. The resistance should be between 200 to 500 Ohms.
• Measure the resistance of the Brown and Orange wires in the large 6 pin connector. This is the primary pickup coil. The resistance should be between 100 to 200 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. If unsure after measurement, you should verify with a timing light. At idle in Neutral the timing marks should align to the ‘FN’ mark. In 1 or 2 the timing marks should align to the ‘F’ mark. Around ~4000 RPM the timing marks should align somewhere between the double line ‘| |’ marks.

⚠️IF ANY OF THE ABOVE MEASUREMENTS READ INFINITY THIS MEANS A WINDING IS OPEN AND THE STATOR NEEDS REPLACED OR REWOUND! CONTACT KIRK AT CUSTOM REWIND IN ALABAMA TO GET IT REWOUND, 1-205-798-7282⚠️

Change Relay Test:
Set your DVM to Volts. Connect the red probe to the Green w/ Red tracer in the 2 pin connector. Connect the black probe to the Green wire in the 3 pin connector. Put the bike on the centerstand and place the bike in Neutral. Turn the key to the “Run” position.
• In Neutral the voltage should be about 0.7V for OEM. It will be much lower than this if you built one with a MOSFET or have ordered one from me.
• In 1 and 2 the voltage should be 11-13V (should be the same as your battery voltage).

⚠️IF YOU ARE UNSURE IF THE CHANGE RELAY IS DEFECTIVE SIMPLY DISCONNECT THE GREEN W/ BLACK AND GREEN W/ WHITE BULLET CONNECTORS COMING FROM THE SIDESTAND SWITCH. IF IT NOW SPARKS THIS MEAN THE SIDESTAND SWITCH IS DEFECTIVE. ADDITIONALLY YOU CAN DISCONNECT THE TWO TERMINAL CONNECTORS LEADING TO THE CHANGE RELAY FROM THE NEUTRAL SWITCH. THE STARTER WILL NOT WORK, BUT YOU CAN USE THE KICKSTARTER TO STILL VERIFY A SPARK. IF IT NOW SPARKS THERE IS SOMETHING WRONG WITH THE CHANGE RELAY.⚠️

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: 0 Ohms or close to that showing the circuit is closed/completed to ground.
• Ignition switch OFF, Run/Kill in any position: 0 Ohms or close to that showing the circuit is closed/completed to ground.

⚠️IF YOU ARE UNSURE IF THE IGNITION SWITCH OR KILL SWITCH IS DEFECTIVE SIMPLY DISCONNECT THE BLACK W/ WHITE TRACER BULLET CONNECTOR LEADING TO THE CDI. IF IT STARTS THERE IS SOMETHING UP WITH THIS SWITCH⚠️

Alternator Tests:

Use the connector with 3 Yellow wires.
• 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.


Stator Crank and Running Tests with PEAK VOLTAGE ADAPTER (Recommended)

• Connect one probe to Green on the 6 pin connector and the other to White on the 2-pin connector. With kill switch OFF crank the bike. It should read about 14 Volts.
• Connect one probe to Green on the 6 pin connector and the other to Blue on the 2-pin connector. With kill switch OFF crank the bike. It should read about 1.2 Volts.
• Connect one probe to Orange and the other to Brown on the 6-pin connector. With kill switch OFF crank the bike. It should read about 2.0 Volts. This is the pickup sensor.
• Connect one probe to Orange and the other to Brown on the 6-pin connector. Start the engine. At idle it should read about 2.5 Volts, it should progressively reach about 2.9 Volts as you give it more throttle. This is the pickup sensor.
• Connect one probe to Green on the 6-pin connector and the other to White on the 2-pin connector. Start the engine. At idle it should read about 219 Volts, it should progressively reach about 300 Volts as you give it more throttle. This is the low RPM coil.
• Connect one probe to Green on the 6-pin connector and the other to Blue on the 2-pin connector. Start the engine. At idle it should read about 232 Volts, it should progressively reach about 240 Volts as you give it more throttle. This is the high RPM coil.
• Connect one probe to Green and the other to Pink on the 6-pin connector. Start the engine. At idle it should read about 1.4 Volts, it should progressively reach about 5 Volts as you give it more throttle. This is the advancer coil.
• Connect one probe to Green and the other to Yellow on the 2-pin on the CDI/coil connector under the tank. Crank or start the engine. It should read about 0.79v. This tests the output of the capacitor in the CDI.


Stator Crank and Running Tests with ANALOG VOLT METER

• Set your AVM to 10VAC range and connect one probe to Green on the 6 pin connector and the other to White on the 2-pin connector. With kill switch OFF crank the bike. It should read about 2 Volts.
• Connect one probe to Green on the 6 pin connector and the other to Blue on the 2-pin connector. With kill switch OFF crank the bike. It should read about 1.5 Volts.
• Set your AVM to 10VAC range and connect one probe to Orange and the other to Brown on the 6-pin connector. Start the engine. At idle it should read about 0.1 Volts, it should progressively reach about 1 V as you give it more throttle. This is the pickup sensor.
• Set your AVM to 250VAC range and connect one probe to Green on the 6-pin connector and the other to White on the 2-pin connector. Start the engine. At idle it should read about 60 Volts, it should progressively reach about 75 Volts as you give it more throttle. This is the low RPM coil.
• Connect one probe to Green on the 6-pin connector and the other to Blue on the 2-pin connector. Start the engine. At idle it should read about 100 Volts, it should progressively reach about 150 to 200 Volts as you give it more throttle. This is the high RPM coil.

CDI Test
There is now a test that can work with digital or analog meters. Please refer to this thread to test it.

If you're still having problems, post here and we can help you go through the tests. I also have a test kit available that I can ship at your expense with a core charge. See the following thread for details: Hondamatic CB400A/CM400A/CM450A Community Ignition Test Kit!.

Rotor Test

Remove the rotor and check that the magnets on the inside grab a small flat head or pick tool. They should grab it with some good force. Conversely, check the "button" magnet on the outside of the rotor. It should also forcefully grab the tool. If it doesn't then the rotor is bad.
 
Last edited:
NB: There is some additional information to add. Particularly from the Change Switch Relay as this has the circuit for the sidestand switch safety. I'll do some more testing with that over the next few days then update the guide accordingly.
 
Updated the change relay test as the expected voltage value will be different if you built one with a MOSFET.

PS: Can we get this pinned?
 
There's an additional test that I've found while working on these for the Blue and White with voltage output readings. This you can do while the bike is actively running to see if the voltage is correct at certain RPM ranges which in turn is fed into the CDI. I'll have to try and carve some time out this week to add it. Being able to test the components as it's running is more accurate than the small voltages that run through the stator from an ohm meter, but it's hard to do so sometimes.
 
Added some very useful tests for use with an analog volt meter during cranking and running to determine output of stator on the bike, which is much more useful data than low voltage ohm readings. Hope this helps others out there.
 
Added a test for use with PVA/Peak Voltage Adapter. The specific brand used was Electronic Specialties 640 Direct Voltage Adapter. Available cheaply on Amazon at https://www.amazon.com/dp/B0093U3TFG. Other brands should give similar output for the CDI, but may differ on the capacitor out to coil/yellow wire. If it differs, let me know.
 
Since selling the CDIs I have gotten a small rash of people who have cooked CDIs (not mine) via the kits. They want these kits in a desperate attempt to solve their issue thinking they can blindly replace the components on the PCB to figure it out.

Every time this has happened the real issue is the stator and it appears to happen after the bike has warmed up and they buy used CDI units cheap and they still fail after a few miles.

This is clearly a stator issue and it may ohm out good on the bench, but in at least one instance the problem was the ground eyelet on the back of the stator was corroded and barely hanging on. Another time one was redirected to one of the mounting screws and also barely hanging on. My guess is that the bike warms up and also with the vibration is constantly floating the ground and the SCRs are intermittently getting the voltage and pickup being sent to it. It happens so fast and the SCRs cannot take this abuse and fail. In one instance I found that eventually the low RPM coil failed open after multiple attempts to rework the board.

Here's what you should do before you buy replacement CDIs if you are cooking them...

  • Rotate the rotor counter clockwise until you see the magnet. If it is rusty, clean it with 320 and then follow up with 400.
  • Inspect the two screws for the pickup coil. Check continuity for this screw to the green wire coming out of the 6-pin canon plug of the stator.
  • While rotating the rotor make sure that it is not dragging on the pickup coil. If it is then it may cause things to short to ground. If the bike has been dropped or the pickup screws have vibrated loose then it may be dragging. If they're not loose and it's dragging then very carefully bend the bracket back into place.
  • Remove the rotor, get the puller tool from Motion Pro.
  • Remove the stator with a JIS #3 T-Handle. Don't try to be clever with the Vessel screwdrivers. You will likely ruin the screw. A hand impact may work, but if you don't do it right you risk breaking the screw or worse. Instead, LASER Tools sells a JIS T-Handle with replaceable bits; get it from Amazon. Mike Nixon also has a set for sale that is a clone of the original Kowa's.
  • On the backside of the stator is a ground eyelet. Inspect it for damage. Clean this area if it appears corroded. If the crimp is barely hanging on or looks corroded then strip it back until you get non-corroded wire and crimp it correctly. Matt at Vintage Connections has what you need. When replacing the screw use BLUE thread locker. Don't use the hi-temp stuff or you'll never get it out.
  • Check the bottom of the pickup sensor. You'll see a magnet. Make sure it's not dirty. Clean with alcohol.
  • Check 6-pin canon plug. Extract the connectors and make sure they are not corroded. Again, if you must, then peel back until you get good wire and crimp. There's a bit of slack so you can trim a little. If it goes too far you'll have to come up with a solution to that. Sometimes, you can see the wires on the stator side. You can attach a tiny clamp probe to it and then check the continuity out of the 6-pin canon plug by wiggling and twisting the harness. If you have more than 1 ohm resistance on ANY of these wires then it's corroded. If the readings are going wild you either have a dirty connector, probes are not attached securely, or you have junky probes.
  • Now, replace the stator and rotor. Re-attach the CDI. Attach a PVA and crank the bike with killswitch set to OFF or disconnect the 2-pin canon plug coming out of the CDI to ignition coil. If you can't do this because it's kickstart only or your starter is weak, etc. then get a drill with a 17mm socket and spin counter clockwise. You should be getting ~150V-200V out of the blue to ground and white to ground. If you don't then a winding is bad. You should be getting some voltage out of the pickup (brown and orange) and advance (pink and green) coils. If you don't, again a winding is bad.
  • If all of this is good, back probe to the yellow and green coming out of the 2-pin canon plug of the CDI. Killswitch set to RUN position. Start the bike if possible; if not then spin with the drill. You should be getting about ~1V coming out of the CDI. This will verify, dynamically, that the CDI is discharging the capacitor. There is no other way to test this. There is no wire combination of bench probing to determine this.

If all these checks come back good, your problem is your ignition coil. Very likely you are using an aftermarket one from eBay. I have seen these ohm out at rest at 5 ohms and the meter goes wild. Crappy windings. Check your caps from these coils. With the same crappy coil I found that it had a very sloppy fit. If your coil is under 1 ohm, caps are good, then replace your plugs with genuine (as in bought it from the dealer, DSS or Partzilla) NGK D8EAs. If the bike starts, runs good for 5-10 minutes then shuts off and won't start again for a few minutes and then instantly dies within 30 seconds your coil is tired and toast. Get a Dyna DC11-2 or the GM coil mod.
 
I just had someone ship to me at their expense a stator, two original CDIs, an ignition coil, and my own CDI for bench testing.

The problem, which could have been solved by slowly going through this guide, was that the White and Blue coil has a bad winding so White to Green and Blue to Green read nothing. The rest reads good and green to the screws show 0 ohms which means the ground itself is OK. The ignition coil is that bad quality 5 ohm coil that ToniAnn also attempted to use. To the person who shipped me these components this is not a slam on you. Rather, I feel bad that there was much wasted effort on your part with frustration for weeks and then spending a lot of money to ship these components to me.

Please, please, please go through the steps. This didn't require a PVA (Peak Voltage Adapter) to diagnose. Simple bench tests with a DMM (Digital Multi Meter) (and you can use a junky Harbor Freight one for this test) made it obvious the problems. I don't want anyone here or elsewhere to have to send me stuff at their expense because they didn't run through the tests or have trouble understanding how to perform the test. If you need help or you think you've ran through the test and nothing works please start a thread with pictures so we can see how you run through the test.
 
Last edited:
Maraakate said:
Please, please, please go through the steps. This didn't require a PVA to diagnose. Simple bench tests with a DVM (and you can use a junky Harbor Freight one for this test) made it obvious the problems. I don't want anyone here or elsewhere to have to send me stuff at their expense because they didn't run through the tests or have trouble understanding how to perform the test. If you need help or you think you've ran through the test and nothing works please start a thread with pictures so we can see how you run through the test.
Click to expand...
For those who may not be completely familiar the term DVM, it's digital volt meter which also measures ohms.

Absolutely agree with above, and it falls right in line with our requests here to show as many pictures as possible when asking questions. They both end the same, to some extent, when not enough visual information is given or when suggested tests are not fully completed. We try to help as much as we can based on the member's information provided, and it can often save the member time and money to be as thorough as possible when showing/describing a problem to us or doing the tests suggested in any diagnosis thread fully and completely. I've said it before, in our forum situation we can only help as much as you allow us to.
 
You reminded me that the terms PVM and DVM may be inclusive to those who never used these tools. I've edited the post accordingly.
 
Another friendly reminder, as this has just happened again. This time someone was pulling their hair out for a month + trying to solve their no spark condition and it ended up being another coil winding open and not being able to interpret the results. Please, please, PLEASE start a thread or ask here before buying any parts, even from me. I really don't want to sell anyone a part they don't need and buy out of desperation to solve their no spark issue.

To any customer of mine that was referred to this thread for diagnostics please register and join the forums. It takes a few minutes and we can all help you solve your problem.
 
Maraakate said:
To any customer of mine that was referred to this thread for diagnostics please register and join the forums. It takes a few minutes and we can all help you solve your problem.
Click to expand...
And to those who are reading this and considering joining, know that it won't take days to get approved - unless you join in the middle of the night in the US (between about 2 AM and 8 AM EST) you'll be approved in minutes, typically well under a half hour. (y)
 
ballbearian said:
I'm sure there is some scientifically quantifiable method of checking it's magnetic force. And a way of restoring it's magnetism.
Click to expand...
Yeah I don't what tools. However, some old Ford Model T guys have found old ~1940s era equipment for re-magnetizing rotors because it apparently was a bigger issue on older stuff. So it is possible, how to do it I really have no idea.

I did take the rotor apart and found that there is a tiny magnet behind the button and it seems to not really have any magnetivity however I see no reason you couldn't find another strong magnet of the same size and insert it and use it again. It just appears to be the individual magnet for the button.
 
McMaster-Carr has a wide variety of button magnets of various materials. I'd have to pull the magnet out and measure it and see if they have something close and if it will make the rotor viable again. I know some XS650 guys have done just this to get the pre-80(81?) year rotors to work on the later years that switched from points to transistorized igniton.
 
esmith250624 said:
Now that would be some serious Redneck engineering.
Click to expand...
Probably would work if the size is right. I've seen people get magnets at the arts and crafts store for the later XS650s that have the TCI units.

The button on the rotor is just a cover. The magnet itself is behind the larger magnet thats held in with the two screws. Pop that off and there's a magnet with a smaller cover hiding behind it.
 
You must log in or register to reply here.
Back
Top Bottom