1990 honda trx300 fourtrax 2X4 no spark - Honda TRX Forum
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post #1 of 30 Old 06-08-2018, 02:39 PM Thread Starter
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1990 honda trx300 fourtrax 2X4 no spark

I've replaced the coil my old one barely tested 1 OHM, the new one tested about 4

I'm not getting anything to the spark plug, I replaced the CDI box, nothing
so I plugged the 2 prong to the CDI box & tested the the 4 prongs cumming out
of the CDI box I'm getting 12 volts out of 3 of them, my question now is,
I'm I supposed be getting 12 Volts out of all 4 prongs



Thank Robert
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post #2 of 30 Old 06-08-2018, 09:04 PM
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Robert, according to the service manual; the first test is for 12 VDC on the blue wire with the white stripe at the CDI unit. The CDI unit is looking for AC voltage from the alternator, so there should be a minimum of 20 to 35 peak volts AC between the yellow wire with the white stripe and ground at the CDI unit when the engine is cranking or running. There should be 12 volts DC on the green wire at the CDI unit. Grounding the green wire (i.e. by putting the transmission in reverse) will limit the output of the CDI unit to limit the reverse speed and turn on the reverse light. There should be an AC voltage on the blue wire with the yellow stripe and ground, but the value can only be measured with a peak voltage tester and no value is listed in the service manual. Likewise, there should be about 150 peak volts between the blue wire with the yellow stripe and the green wire at the coil with the wires unplugged from the coil.

Let's address the coil ohms - at 68 degrees F (20 degrees C) the primary (the black and green terminals) is supposed to check .1 - .2 ohms. Testing the secondary of the coil is more involved; with the plug cap attached to the plug wire, measure between the terminal inside the cap and the green terminal on the coil - you should measure 8100 to 10k ohms. With the plug cap removed, the coil should ohm out at 3600 to 4500 ohms.

Just follow the step by step procedure in the service manual and you will probably be up and running in a short time.
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post #3 of 30 Old 06-09-2018, 02:45 PM Thread Starter
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There's no mention of the Black wire with Yellow strip, this one goes to the coil
I get nothing no matter what I try


blue wire with the white stripe I'm getting 9.9 V
yellow wire with the white stripe I'm getting 11 V when I turn the engine over it drops to 8 V
the green wire at the CDI unit I'm getting 11 V

the blue wire with the yellow stripe 11 V


the black and green terminals on the coil I get 1.1
With the plug cap removed 2.28

I don't know what part/parts are bad



Thanks Robert
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post #4 of 30 Old 06-09-2018, 05:15 PM
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The black wire with the yellow stripe goes from the CDI unit to the coil. It will have a minimum 150 volt pulse each time the pulse generator tells the CDI to fire the spark plug. The pulse is milliseconds in length and has to be checked with an oscilloscope or a peak voltage tester.

What you are trying to do is fix something without having the right tools. It's like trying to to catch a mosquito with a fish net.

There's only 5 parts to the ignition system; alternator, pulse generator, CDI box. coil and wiring. Forget about the switches and concentrate on the basics.

You said you got a new coil and a new CDI - the coil is just a transformer and easily tested - where did you get the CDI box?

There are no tests for the CDI box other than replacing with a known good one. With an o-scope or a peak voltage tester you can measure and observe the inputs and outputs at the CDI box.

Precautions listed in the service manual: 1) Never disconnect any electrical connections when the engine is running 2) Apply Dielectric grease to all electrical connectors prior to reconnecting them to help seal out moisture 3) Make sure all electrical connectors are free of corrosion and are completely coupled to each other 4) Do not substitute another type of ignition coil 5) The DC-CDI unit is mounted within a rubber vibration isolator. Always be sure that the isolator is in place when installing the unit.

NOTE: Honda does not provide any service specifications for testing the DC-CDI unit. They provide only test procedures for the components within the ignition system.

First there should be 6 wires going to the CDI unit (4 wires in one plug and 2 wires in another plug.

You need 12 vdc on the blue wire with the white stripe (or black wire with a white stripe) at the CDI box (the wiring diagrams in the service manual indicate a black wire with a white stripe in one drawing and the b/w wire changing to a blue/white wire in another drawing) - if you have this, you have just eliminated the kill switches, fuses and battery as a problem.

You should have 12 vdc on the gray wire at the CDI box - if you do not have voltage on the gray wire, check the clutch diode in the wiring harness

There should be 18-45 vac on the yellow wire with the white stripe when the engine is cranking or running

There should be a pulse from the pulse generator on the blue wire with the yellow stripe

Dark green should have continuity to ground

The black wire with the yellow stripe goes to the coil

If the coil is new and the CDI is new that only leaves the pulse generator, alternator stator and the wiring

A friend of mine was troubleshooting a no spark issue on his 86 XR200-RFVCC many years ago. He used my meters and the Honda service manual - the only part that tested good was the stator, so he replaced the pulse generator; still no spark - he then replaced the coil; no spark - he replaced the CDI unit; no spark - he replaced the stator; SPARK!. He put the old parts back on one at a time, still had spark - it turned out the only part that tested good was the bad one.

Good luck, I think I have detailed the entire procedure to help you get your ignition system fixed. NOTE: all testing should be done with a new spark plug.

PS - in my previous post I mis-identified a the gray wire as a green wire

Last edited by Here 2 help; 06-09-2018 at 05:20 PM.
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post #5 of 30 Old 06-09-2018, 05:25 PM Thread Starter
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I got the CDI box off ebay, (might be the problem cheap junk) I'll check the other later
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post #6 of 30 Old 06-09-2018, 05:33 PM
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You just need to know if the CDI unit is AC or DC - They are the same size and have the same number of pins
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post #7 of 30 Old 06-09-2018, 07:43 PM Thread Starter
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The new one is smaller, same # of matching pins,
how do I tell if it's AC or DC?
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post #8 of 30 Old 06-09-2018, 07:49 PM
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Cdi

Quote:
Originally Posted by Thepatientone View Post
The new one is smaller, same # of matching pins,
how do I tell if it's AC or DC?
The seller should advertise it as AC or DC - just having the same plugs and number of pins is irrelevant. Go back and look at the ad where you bought it from.
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post #9 of 30 Old 06-09-2018, 08:30 PM Thread Starter
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Quote:
Originally Posted by Here 2 help View Post
Quote:
Originally Posted by Thepatientone View Post
The new one is smaller, same # of matching pins,
how do I tell if it's AC or DC?
The seller should advertise it as AC or DC - just having the same plugs and number of pins is irrelevant. Go back and look at the ad where you bought it from.

I checked the listing no info there, tried to trace the UPC code, no luck, it would be a waste of time to contact the seller, these sellers no nothing about there product, unlike me, I'm retired, & I know everything about the products I sale & 99% of what I sale is made in the USA.


I can wire a house but when it come to figuring out electrical problems I'm lost



Thank for all your help
Robert
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post #10 of 30 Old 06-09-2018, 09:04 PM
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Great info. I came on here cuz I'm having the same issue with an 88 fourtrax 300 2x4. Am I safe to assume that all the info here would apply to my 88? Thanks!
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