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Louie
Louie, Technician
Category: Motorcycle
Satisfied Customers: 11438
Experience:  25+ yrs. experience
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1990 honda trx300fw atv. no start on power from cdi unit.

Customer Question

1990 honda trx300fw atv. no start on power from cdi unit.
Submitted: 4 months ago.
Category: Motorcycle
Expert:  Louie replied 4 months ago.

Hi Richard and welcome to JustAnswer,

Thank you for the question and your patience. Should you still need assistance for information purposes only...

Initially, would the described symptom of "...no start on power..." be that the Honda would not crank? If yes, then proposed preliminary tries (if have not been done):

  • check (or better yet, replace) the two (2) 15A fuses connected inline with the red & pink/white wires;
  • locate the starter relay, start by following the big cable from the + terminal of the battery as it always ends up tied to 1 of the 2 big terminals of the starter relay.
  • jump the 2 big terminals of the starter relay;
  • Expect a big spark;

  • If it does not crank, then possibly a cable and/or terminal issue;

  • if it does crank, then ensure that its green/red wire has a good ground connection while in neutral or the clutch lever pulled in;

  • and that its yellow/red wire gets a +12V when pressing on the starter button;

  • if there is good ground and IGN+12, then there should be a click from the relay;

  • no click, ground or IGN+12 missing or relay faulty;

  • there is a click but starter motor would not spin, then relay would be suspect;

  • no IGN+12, then check the wiring, connectors and switches;

  • no good ground connection on the green/red wire, consider test hardwiring a second ground line;

  • Actual wire colors may vary depending on versions / mods.

Customer: replied 4 months ago.
Hi Louie, thanks for the reply. I have not used this company before and I did not understand the correct answers.
So having said that. My problem is cranks but no start. This year atv 90-92 has a special wiring. I have no spark to the spark plug no electricity to the coil(BL/Y wire) from the cdi unit. I have 12 volts to the cdi unit ( BL/W wire) with the key on. There is 12 volts at the (Gr wire) at the cdi unit. Is there supposed to be 12 volts at that wire with the key on? I have a good cdi unit because it is new and works correctly on another atv. You may want to study the wire diagram on this bike. 1990 TRX300FW VIN # ***** 1503 LA 208667. Also the procedure for no spark at the plug says to check the alternator sense wire, I am not sure what wire that is because this bike does not have the color wire mentioned in the test procedure. How do I test the alternator wire, it appears the cdi unit requires a signal from the alternator before spark to the spark plug happens.
Thanks Richard.
Expert:  Louie replied 4 months ago.

Yes to the phone call request Richard but bear with me and let's work out the basic information prior to the call

Offhand, on a 'no-spark' issue and the above additional information:

  • no electricity to the coil(BL/Y wire) from the cdi unit - has to be pulsating when attempting to start;
  • 12 volts to the cdi unit ( BL/W wire) with the key on - IGN+12V from the Engine Stop switch;
  • 12 volts at the (Gr wire) at the cdi unit. Is there supposed to be 12 volts at that wire with the key on? - green wires are almost always tied to ground;
  • study the wire diagram - to serve as common reference, please upload a copy of the diagram to Dropbox or imgur;
  • check the alternator sense wire - the stator has 3 wires of similar color often yellow (or white). Any of these 3 wires may be used for the CDI's alternator sense wire;
  • How do I test the alternator wire - any pairing of yellow-to-yellow should produce a low Ω reading. None of these wires should show a continuity to engine ground;
  • cdi unit requires a signal from the alternator - yes, actually 2 signals; 1 from the stator and the other from the ignition pulse generator coil co-located in the stator area.
Customer: replied 4 months ago.