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TRX 300fw Starter issue

879 Views 12 Replies 4 Participants Last post by  retro
So I am working on my project ATV and now i am to the point where I am reinstalling the battery and body pieces.

Before this part the ATV sat in a shed for about 3 years, up until like a week ago.
My issue is as follows:

As soon as I add ANY power to the atv terminals (battery connections, positive to the top of starter, negative to engine casing under carb) the ATV instantly tries to auto-start using the electric starter. I thought the button may be corroded so i uninstalled and cleaned it, but no luck, So then I COMPLETELY unplugged the starter button and the ATV still automatically starts turning over.

All other lights and switches work as normal, but as soon as I give power via a battery or charger, it attempts to start.

Any ides?

ps: I did NOTHING to the electrical system, it is all stock.


Edit: Upon working on it today, i think that there is the possibility the electrical system was worked on incorrectly from the PO i got this from.
I added some pictures (sorry i have no flood work lights, i work in a shed with no electrisity using head lamps) of the electical system in the rear, and terminals on the starter and engine ground.

What do you guys think? I cant read a wireing diagram so i have no clue if it is still wired up "stock", but there were alot of wires that had odd spots burt and taped over, and strange connectors that do not look professionally done
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You need a replacement wiring harness and possibly a solenoid. That one is probably gonna fry expensive stuff if it hasn't already.
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The service manual... takes only about 30 seconds.
One more question, On the harness for the tail tight, i have a pink wire. I THINK i found it on the wiring diagram as " P (option)" near top right.

What does that go to (if its not optional) and/or what is it for (if it is optional)?
That is an accessory wire tap that supplies positive battery voltage while the key is turned on. It can be used to supply power for tools or equipment attached to the rear rack such as sprayers that farmers might use, or any other low power device. So its use is optional like you thought.
The max alternator output is listed in the specs as 0.22 kilowatts (220 watts) @ 5000 RPM. So converting 220 watts to amps at a nominal charging voltage of 14.5 volts DC = 15.172 amps gross. But there are losses in every electric circuit due to resistance through wiring and components, so the net amperage available at 14.5 volts will be less... We have to guess until we measure, so lets pick a reasonable figure... say 14 amps max at 5000 RPM. Any engine speed lower than 5000 will supply less than 14 amps. So with an idling motor having a fully charged battery with only the neutral light being powered, you might get somewhere between 2-4 amps max. Voltage will drop from 14.5 down to where the battery begins to supply amperage to the circuit as accessory loads increase.

Note that inverters might only be 70%-90% efficient at converting DC to AC depending on the design and quality of the unit. So expect huge losses while powering an inverter. On average a small cheap modified sine wave inverter might draw 100 amps at 12.8 volts DC to provide 7-9 amps at 115 volts AC, for example.

So, the charging system on your bike is not capable of powering an electric chain saw that requires 115 volts AC... but it will recharge your inverter battery (slowly) while you are riding around in the woods looking for another tree to dismember. :)

If your bike has an accessory fuse all DC loads you connect will be limited to the fuse rating. The ATV battery should not be run dead ever, as deep cycling causes loss of battery capacity and leads to very early failures. It wasn't designed to be deep cycled.

Have fun!
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