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1993 ZX750 electrical problem?

Discussion in 'Technical and Troubleshooting Torque' started by taken670, Nov 10, 2015.

  1. Hey everyone, I'm trying to diagnose a big problem with bike.
    My bike is over 20 years old and has done over 100 000 km, so granted I am going to have a few problems.
    I just got new chain and new front and rear sprockets and also had the mechanic fix a headlight problem which was the wires had burnt out. When I went to pick up the bike, it would not start at all, the lights would not even come on the dash, so I ended up buying a new battery and new solenoid and the lights all came on, though sometimes I had to roll start the bike. I then took the bike down for a ride through Bundeena and the royal national park, If you have been there you know the road is really bumpy in parts. When I was coming back from there I started losing power (it felt like I was running out of fuel, though I knew I wasnt) so I pulled over, I revved it a few times and it was all good. When I was coming home through the city I noticed I had to keep the revs up with my hand so the bike would not die. Early the next morning, I rode the bike to work and got to a set of traffic lights about 3k from home and the bike just died. No power at all to the dash, the bike does not kick over, the immobilser does not beep, I cant even roll start it. I have bought a multimeter and have been testing the bike, I have taken off all the fairing and everything so I can have good access, I cant see any pinched or burnt out wires, the main earth has a current and so do the wires. Ive been trying to work it out for nearly 2 weeks now. Any hints? Thanks

  2. With it running you need to see 14 volts across the battery at 2500 revs or so for it to charge the battery. Less than that and your running on the battery till it gets to low and stops.Have you fully charged the battery,do that and hopefully it will start and you can check the charging. Less than 12 or more than 14.5 and your regulator has dieded. If that's not it it gets complicated then. Do you have a battery charger, they are absolutely a good thing to have, especially Intelligent trickle chargers for bikes that sit around a bit. Make sure it also does a strong blast type charge capacity as well.That is handy in some charging applications.Good luck with this, green smoke escaping the wires,my explanation for missing electricals, is a real pain to sort,
    • Agree Agree x 1
  3. Hey Zim, thanks. Yeah it is a pain because I cant start it to check, though the battery is only about 2 weeks old. Since I have been trying to diagnose the problem, I checked the battery voltage and I get about 12.8.
    Yes trying to find the problem is a nightmare!
  4. I tend to agree with Zim that it is not charging which points to regulator or alternator. 12.8 is a healthy voltage though (provided you can trust your multimeter to be within 1% accurate, if it is a cheapy then perhaps not)

    Borrow a battery charger, a low power one if possible, charge the battery, Note don't leave it overnight on charge as you can overcharge. Then start the bike and measure the voltage at Revs as suggested by Zim.
  5. For starting go back to basics, make sure you have fuel, kill switch right,side stand cut out or clutch cut out. Check for spark on all 4.Find the starter motor and give it a wack with a lump of timber while pressing the button,firm wack but dont go nuts they stick sometimes.Brand new batteries sometimes die as well,jumper leads from another battery.Is it spinning over at all.
  6. ^^^ This
  7. Yeah I see what you mean. My multimeter was 20 dollars from bunnings, so its not a great one, however all the readings I have taken on the bike are roughly the same - so at least its not jumping around everywhere. Yep I have a battery charger, so i'll charge it tomorrow - thanks. though i really dont think it is the battery because i cant even roll start the bike aand it dosent even kick over.
  8. yeah, ive taken the tank off to get better access to the innards. no the bike does nothing, when i turn the key absolutely nothing happens, no dash lights (oil and neutral), no headlights. I checked the main on/off switch today and it had a current going through it, but when i press the start button, there is nothing. I have checked the stand cut out (it only cuts out when you engage a gear). I just feel so dumb I cant find the problem lol, i know it has to be something major- right under my nose!!!!
  9. Rec-reg's dead.
  10. I have been trying to localize the problem but I cant seem t
    hehe, i googled rec reg and got recreational registration??
  11. Regulator/Rectifier It takes the AC voltage the alternator produces turns it into DC and maintains the voltage within limts to charge the battery.
  12. If its not showing anything, main fuse. There is one in some starter solenoids as well. Its hard to see in some cases. Try tugging on any lumps on the solenoid and it might be a fuse. There is a spare fuse mounted on mine as well.
  13. ok so i'll charge the battery up to about 14 volts tomorrow and see where i go from there.
  14. #14 Zim, Nov 11, 2015
    Last edited: Nov 11, 2015
    The battery with only show 12 volts,maybe 12 .2 connected to the bike engine off . Thats a fully charged battery. It will only show 14 when its down on charge and connected to a running bike with the engine revving above 2500 rpms,and the alternator is topping the battery up in juice the faster the engine spins the more electrical juice is made.. Its worth turning the lights on with it revving as well. It should still show 14 even with the engine taking battery power and the lights taking battery power as well.That's the regulating bit of the regulator so your alternator tops up the battery as its juice is used to start and run the bike, and not over charge the battery when the battery is fully charged . The alternator has the capacity if its fully ok to add 16 17 even 18 volts to the battery and get it red hot and explode even but the regulator stops it at 14 and a bit.If your lucky its the Regulator that's dead and not the alternator,it gets more complicated if it the latter. BTW if the battery shows around 9 or 10 volts it wont have enough punch to spin the motor and spark the plugs, you need both for a start.Sometimes they have enough to spin and not spark.My head hurts now, that all the green smoke stuff I know, and that isn't much
  15. yeah I've put my bike on charge now, so i'll have a look in a couple of hours.. I actually do have a spare alternator for this bike, so it will just be a matter of installing it. does anybody know what that 'W' and 'B' stands for on the main fuse/solenoid?
  16. Sorry, its actually an "M' and 'B'. When i bought the new one, the M and B were on different sides.
  17. No, it should be on your circuit diagram though. I would guess B is battery but without any evidence to say that is so.

    Edited to Add: M may be Motor then as in starter motor. These are the large heave connections on the solenoid are they rather than the smaller lighter ones?
  18. That makes so much sense it is not funny. Cheers
  19. ok so finihshed charging the battery, it only needed about an hour, and checking afterwards it reads about 13.8 volts. I tried to start it while giving the starter motor a whack and nothing. no lights, no kicking over or anything
  20. so just did some more tests. i put the + end on the battery pos terminal and then the negative end on the cable in the junction box that come from the IC igniter, there seems to be very low (0.8 voltage, that seems like could be something. Also the the sidestand cable had 0 volts, but im not sure if it should or not because also the fan cable had 0 volts, so maybe they only get voltage when they are used