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98 trx300fw electrical problem

3126 Views 11 Replies 6 Participants Last post by  SamUK
Got a electrical problem that's beyond my skill level. Got a 98 trx300fw that I had Givin to me with a bad CDI BOX. Bought a new OEM box and started the bike. Within seconds it shorted the box out. Expensive couple of seconds. Any thoughts on what problem I might have and if it's even worth messing with.
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Ouch! Get a copy of the FSM if you haven't yet, there are wiring diagrams in the back... I imagine the wiring has been altered or something is hooked up backwards? I suppose the regulator/rectifier could be shorted too, allowing raw AC voltage into the CDI. Run some tests on the stator windings and regulator to look for shorting and look for bare wires rubbing on the frame. If the wiring diagram shows any diodes are in the electrical system, check those too.

The FSM is HERE.

I would start at the battery & solenoid and go through the entire harness looking for problems. Put eyeballs on the ignition switch harness to make sure someone hasn't swapped in the wrong switch or cobbled on it. Put the same eyeballs on the kill switch harness plug. Check for missing diodes etc.
Check the frame ground for the wiring harness too. There is a diode that protects the CDI:

Let us know how it goes...


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