Running on only 2 cylinders

[Guest]

I got my 85’ Aspencad running yesterday but discovered that cylinders 3 & 4 (rear ones) were not getting any spark. Pull the plug wire and it had no effect on engine operation.

I did an ohm test against the two coils and their primary and secondary resistances are very close two each other. I ohmed the pulse generator coils and they matched each other too. Voltage is found at the blue/yellow wire at the left coil (as you ride the bike)

Any other tests, or do I start searching for a CDI module?

Thanks in advance.

Brian

[Ed Z]

When I got my bike it would intermittently run on two cylinders from time to time... Pulled a bunch of hair out trying to find out why (hard to test for a fault when it's not present)... What I found was one of the female connectors on one coil was not plugged in correctly, but rather was just resting between the plastic insulator and the connector... If I hit a bump just right it would shift and loose contact (thus run on only 2 cylinders)... If the pick-up coils and the primary coils ohm out OK, then it likely is a connection issue... Do check for voltage on both of the primary coils (you stated only having voltage to one wire)... You may have a wire shorted to ground somewhere (insulation bad) or a break in one (could be internal only (i.e. insulation still intact)...

Here's a place to get wiring diagrams and electrical manual for free...<!-- m --><a class="postlink" href="http://www.goldwingdocs.com/">http://www.goldwingdocs.com/</a><!-- m --> (Scroll down the page to get the manual you want)

[Guest]

Thanks for input Ed.

I did further testing and it seems to be the CDI module. There is power at both black/white wires. The coils have simular ohm readings and do the plus generator coils, and I have continuity from the coils to the CDI plug.

The local Honda dealer stated "Replace with know good part" as the only way to verify that the module is bad.

By the way, unless the manual has been recently updated, like the last three days, the manual is miss serveral pages, most of the ignition section.

Brian

[Guest]

The local Honda dealer stated "Replace with know good part" as the only way to verify that the module is bad.

There is at least one test you can do to verify the cdi as the problem.

Check the voltage at the b/w wire on the suspect coil. It should read 12v. with the ignition on. Probe the other terminal of the coil with the negative lead of the meter and crank the engine. You should get a fluctuation in voltage of OVER one volt. If you do, the cdi is pulsing ground for the coil. If you don't, you have a problem in the primary circuit. Since you have checked continuity to and through the rest of the circuit, the cdi is at fault.

Another check is a simple visual inspection. Since the bike starts and runs, the fuel pump is operating. The fuel pump relay gets it's ground from the same wire at the cdi as one of the coils. This should mean that this leg of the cdi is good. The tach signal is driven from the other leg. Does the tach work? If the fuel pump operates AND the tach works, this would indicate the cdi is functioning. Are you positive you have NO spark?

[Guest]

I verified that there was not any spark but using an inductive timing light. I had timing light flashing (spark) on the front two cyclinders but not the rear two.

Sadly, I think I damaged the CDI when I mis-read the trouble shooting book. I bypassed the fuel pump relay with a jumper. #-o This jumer connected all leads of the relay connector to the input voltage from the fuse box. Therefor, voltage from the fuse box was connected directly to the blue/yellow grounding lead of the CDI. You were kind enough to correct my error by explaining the circuit's operation to me. I have since corrected this issue, but the spark problem persists.

Thanks for the testing suggestions.
Brian

[Guest]

If your fuel pump still runs, the cdi is okay....remember, it grounds the relay.
I really don't think you have a cdi problem, most problems associated with the cdi are complete failures, or improper application of the timing advance.
Put the voltmeter away for a minute and use an old fashioned test light. This is a 12v circuit so you won't do any damage.
Connect the test light to ground and probe the B/w wire connector at the coil. Crank the engine. The coils will fire with voltages above 9volts. Nine is enough to light the test light. If it goes out while cranking, you have a short or insufficient current supplied to the coil.
If it doesn't change while cranking, you have an open (probably not because you said you had continuity). If it flickers, it indicates the voltage is varying and the primary circuit is okay.

[Guest]

GL,

I was not able to connect to the blk/wht wire of the left coil, but I was able to get a connection on the blu/ylw wire which leads to the CDI module.

My test light did not flicker when cranking. It did dim slightly do to the electrical load of starting. I have removed the headlight fuse to provide a higher voltage when cranking/testing.

From this I have to surmise that the CDI is not closing the primary coil circuit to ground that would cause the plugs to fire. Therefore, it’s either the CDI or the plus generator failure. However, I have similar ohm readings of the plus coils when checked at the white plug that connects to the CDI.

Do you know of any way to determine that the plus coil is generating a plus? I would imagine that this is very low current/voltage and could only be read with an oscilloscope. Do you think a digital voltmeter would see it?

Thanks for working with me on this problem.
Brian

[Guest]

Let's start over.
Since you bypassed the relay incorrectly, does the fuel pump still operate or the bike start. I know you don't have fire on 3 and 4, but does the bike start?
If so, forget about the cdi unit. The pulse generators send a signal to the cdi. If they weren't working, the cdi would never ground the coil circuits, and the bike wouldn't run.
Does the fuel pump still work correctly?

[Guest]

Starting over:

1) The fuel pump relay is bad. I have bypassed this and it now works independently from the ignition system. The blue/yellow wire from the fuel pump relay is not connected to any thing.

2) There is voltage at the blk/wht terminals for both coils.

3) The ohm readings of the secondary windings of the coils are very simular to each other, but a little high according to the Honda shop manual.

4) The ohm readings of plus generator coils are very simular, I do not remember if they are in spec with the shop manual.

5) I have continuity through out the ignition wiring harness up to the connectors coming from the CDI.

6) Using a light tester: When it is connected to the yellow/blue wire coil terminal and the ignition switch is in the ON position, it shines brightly. The light will flicker when cranking the engine. When it is connected to the blue/yellow wire coil terminal and the ignition swithc is in the ON position, it shines brightly. It does not flicker when cranking the engine.

The only thing I can not determine is weather or not the left plus generator is creating a signal for the CDI. If not, the CDI will not fire the rear plugs. I am going to build a simple LED tester and see if I can get a plus signal from both generators.

Brian

[Guest]

Oh, I forgot. The bike starts and runs on two cylinders.

[Guest]

Maybe I misread your original post? If the bike ONLY runs with the fuel pump relay BYPASSED, it is quite possible you have a bad cdi or pulse generator. Your relay may be okay once it gets the proper ground circuit? Sorry for the confusion.

[Guest]

GL,

I used a simple LED to verify that the plus coils are generating a signal. How much, what voltage I can not determine at this point. The LED requires very little current to excite it, therefore it makes a poor man's low current tester.

I disconnected the lead coming from the front of the engine. Determine what two sets of pins created a circuit with the ohm meter. Placed the LED leads in to the two connectors and cranked over the engine. The LED flashed as the engine turned over for each set of connects which cause me to belive that my CDI is at fault.

"When you have eliminated the impossible, whatever remains, however improbable, must be the truth." Sherlock Holems

What type of bike do you think he would have rode? :lol:

Thanks again for all your help and suggestions. I learn a lot.

Brian

[kbgl1200]

Did you ever fix this problem? I had a similar problem and found my coil was bad. Shorted primary winding causing too little resistance in the coil and burning the transistor in the ignition control unit. I didn't want to pay 380.00 for new and 150.00 for used so I researched the transistor and found one to replace the burnt one at radio shack part #tip120 . I installed the transistor and reinstalled the icm and she runs like a Swiss watch. Oh I installed a new coil as well. I bought two of the transistors for under four dollars.