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1979 KZ 250 Electrical System Upgrade

Discussion in 'Maintenance and Servicing' started by Webby95, Jan 19, 2016.

  1. Hi all,

    Purchased this 1979 KZ250 as a project and its been coming along beautifully. Fabricated a new bracket/mount for a new battery (old one rusty), new spark plugs, new brakes, rebuilt the carby's and fixed the clutch cable. All this has been made easier by the fact that i have found the workshop manual. SO far its had all the advice i've needed, until now. The wiring on this bike is a mess. 90% of it is one colour connected with masking tape with colours written on it with whiteboard marker. Safe to say i'd be laughed out of the building trying to get a RWC. I've taken off the entire electrical system, mostly in one piece, in the hopes of upgrading it. I don't want to copy it because i cant trust that it was done correctly. I want to replace all the components and join all wires correctly and use decent wire. Turning the key turns the bike on and then you're SUPPOSED to need to press the START button but somethings gone wrong in there somewhere and most of the time the engine fires up at the turn of the key. I definitely need a new starter switch. Does the regulator/rectifier remove the need for a fuse box? i was surprised that there wasn't one on there already. Advice on the correct wiring/fuses/ignition system/connectors? Cheers all
    • Like Like x 1
  2. The rectifier bit turns the AC out of the alternator to DC, the regulator bit limits how much voltage goes to charge the battery to prevent it being cooked.

    You still need fuses or if things go wrong you will end up burning out wiring and/or frying various electric/electronic components on the bike, most of which have the annoying characteristic of being expensive to replace. And if you are really lucky, your bike will catch fire.

    Fuses are your friend. Although in a pinch you may be able to substitute a 17 mm bolt. :whistle:
  3. awesome thanks for your help mate! one thing im struggling to grasp is grounding to the chassis. i get what it does and how it works but the actual set up is confusing me. The neg terminal of the battery is connected to the frame which means that all electrical accessories can be grounded to the frame, right? does that mean every accessory has a connection touching the frame? im not sure why this is confusing me so much, im usually pretty 'switched on' ;)
  4. Yep the frame acts like a big heavy duty inflexible bit of wire to complete the circuit. This means a lot of things can have only a positive wire going into them and are earthed through the frame. However not necessarily every accessory. On my bike, the horns have an negative wire and aren't earthed directly to the frame. However on my partner's bike the horns are simply bottled to the frame and have a single positive wire.

    And I have seen reg/recs which use the frame for earth and others which have a separate negative wire. Dunno if there is a particular advantage of one system over the other or not.
  5. Bear in mind that the steering head bearings do not generally provide a reliable path for current so you either need a big earth connection wire from forks to frame, or anything mounted on the forks (instruments, lights etc.) needs an earth connection back to the frame in the main loom or it might not work reliably.
  6. Thanks heaps folks! It is coming along nicely. Got it all laid out with the wires that need to be replaced ready to go. Almost everything ive read though has told me that i NEED to replace the reg/reg and ignition coils to go with my new battery. When i went to go and buy them i more or less got laughed at for trying to buy these things. I was told that 'if they work don't bother replacing them, youre just burning money'. I suppose thats not totally rubbish advice but do you think i can get away without replacing them? it would mean that im pretty much just replacing the battery and getting rid of the corrosion on the contact points.
  7. I would only replace either bits that are stuffed or look like they are about to become stuffed. The parts you are talking about could give up the ghost tomorrow but may last ten more years. You could replace them on the assumption it wil be more reliable and some thing else could go kaput and leave you stranded on the side of the road.
    If it ain't broke I wouldn't touch it. Put the savings into fuel and have fun.
    • Agree Agree x 1
  8. Up to the final (and what i thought would be simplest part of the electrics), the switches. I bought a new
    50311070000 for the lights, horn, turn signals and kill switch and cannot for the life of me match the switches to the wires. So far the indicators are fine but the horn works when you press the kill switch, there is no highbeam/lowbeam, just on. I've searched all over countless websites trying to find which colour wires connect to which switches and wasted hours on trial and error. If anyone knows which colours connect to which switches ill then be able to connect them to the correct wires on the rest of the bike. Id like to avoid pulling the switch apart too.
  9. I think I might have the manual in pdf form somewhere (kz400). Let me have a look on my computer at home.