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cbr250rr electrical issues

Discussion in 'Technical and Troubleshooting Torque' started by disassembled, Nov 21, 2007.

  1. Hey people,

    I thought i'd ask this question after many hours of pondering on this problem without a great explaination.


    1. Battery losing charge, ofter while riding to the point of the bike shutting down after a long day out riding, or behaves like there isn't much spark (eg: not revving, stalling on throttle open and so on)

    2. Dimming headlights while at idle, and/or indicators on

    3. Sometimes bike won't start due to lack of charge

    (Ok I know what the above point to but... this one has be a bit confused )

    4. Main fuse physically melting, but doesn't burn out.

    The battery has been replaced recently, after these symptoms started occuring, and It wouldn't suprise me if it was stuffed again anyway.

    Ideas i've come up with.

    1. Faulty reg/rec
    Checked voltage, and seems to be within spec at worst a tiny bit lower than it should be. Although it may be possible that the rectifier is only doing a half wave rectification and that may be having some strange effects.

    2. Bad connections somewhere
    I've been over most of the power connections for signs of a bad connection or corrosion, but nothing obvious. I've also cleaned the major connectors.

    3. Excessive resistance in the starter solenoid
    The main fuse it located on the starter solenoid module. I though it might be possible that there was too much resistance in the solenoid, and the unit was getting extremely hot, transfering heat to the fuse, and therfore causing it to melt. Although though something else should be showing signs of damage

    4. Solenoid not completely disengaging
    This would explain the lack of available current, if the solenoid was staying slightly engaged, say enough to draw current, but not make a connection to the starter circuit. Again, this has the same implications as above, however I would the the coil would have burned by now.

    5. Battery somehow pulling excessive current...
    Not sure about this one, perhaps maybe.

    That's it, I hope someone has some better ideas than me, or might have a similar experience.

    Edit: forgot to ad that the bike normally runs fine, and starts fine on a freshly charged battery. (Obviously the battery is draining or not charging, bike will usually clutch fine, so it's getting some power from the generator?)

  2. Sounds like a high resistance joint at the "main fuse" if its getting hot enough to melt it , would also account for low charge to battery.
  3. If there is around 14.4V at the battery, with the engine running then the regulator is ok.
    A melting fuse mean a high resistance somewhere close. Check all connections.
  4. Yes, on the fuse itself!

    If the plastic holder for the fuse melts the fuse itself has a bad connection(s) to the wires which connect it to the rest of the wiring. Fix em!


    Trevor G
  5. Haha, yep. Will check the terminals and see what the multimeter has to say about it. Might as well change them anyway.

    Bike is at the spanners at the moment having a major service, i mentioned it to the mech, and he looked a little confused, but is going to look into it.
  6. At the start I was thinking it could be reg/rec. But if the fuse has melted like that I'll check the fuse first...
  7. Here's some more to the riddle.

    Symptoms as above in first post.

    Firstly... Here's what the melted fuse looks like

    Here's the wiring diagram of the affected area

    Now, due to the fuse being physically metled, and not actually burned, the only conclusion i can draw is that the starter solenoid/main fuse module is getting physically hot. Now this could happen for only two reasons in my opinion. Either, the internal resistance of the unit is extremely high, or the coil on the solenoid is staying partly energised, and drawing current continuously.

    I've checked the internal resistances, and they all seem to be ok (.1-.2ohms). Just thought about the solenoid coils so i haven't checked that possibility yet. However that would have to be caused by either an internal short from the positive battery terminal, or the charge output from the reg/rec, or a short in the start button circuit. Could only be slight though.

    These don't really explain the undercharge of the battery. I checked the charge voltage and it was between 13.8v-15v (ok). It actually seems like it might be intermittent. If the increase of temperature gradually increased the resistance from the output of the reg/rec, back to the battery, this would cause a drop in charge voltage, and cause the battery to not charge.

    I'm a little stuck on this one, Any opinions? Suggestions?
  8. From the melted plastic and NO physical evidence of actuall burning at the fuse contact I'd say the high resistance joint is on the wire that joins the fuse terminal. You may have to replace the unit that it lives in :(
  9. That's what i was thinking, although i wanted to hear someone else come to the same conclusion.

    Tried to pull the module apart today, but it's well and truly sealed.
  10. 1+ +1



    Look for a wire which is unravelling or untwisting, with melted or burnt insulation. You must bypass/cut off any wire that is not perfectly bright copper in appearance and with soft insulation.
  11. Was thinking of replacing the whole wiring loom from the reg/rec to the solenoid, battery anyway. Not alot of work to do it.
  12. Well I've picked up a replacement starter solenoid/main fuse module from the wreckers. Looks ok to me, will install it on the weekend and see how it goes.

  13. Well, replaced the old solenoid tonight. Decided to solder the pigtail lead which came with the replacement unit from the wreckers onto the loom. No problem...

    Managed to solder up the wires without putting the heatshrink on to start with...

    Cut off wires, re strip.

    Put heatshrink on, resolder the wires. Goddamn it, had the vent from my gas soldering iron pointed at the bloody heatshrink. Shit!

    Ok, will go and look for some insulation tape. SHIT stepped on the glass i had sitting near me (it's getting dark now, can't see anymore). No more drink for me :(

    Ok, better go look for this tape, so i can get everything back together. No idea where the tape went.

    Oh well, guess i'll just roll the bike back up the grass from the garage to the back yard where I store the bike. Get about half way up the wet lawn and slip over. Over goes the bike.

    Pick it up, it's kicked into gear, no visible damage... GREAT! Oh no cracked side fairing where there were some previous repairs, bugger.

    Though i'd better finish the job, so went off and found some insulation tape, and cleaned everything up. Check again i got the wires all ok, cool all good.

    Fired her up and i SWEAR the bike it running better. Didn't have to ass around with the choke to get it idling. She's idling smoother than before, revs are holding better, less dimming of the lights. Checked the charge voltage 13.2v at battery, 13.3v at reg/rec. (Is this voltage drop ok?) There seems to be about .3 ohms resistance, which seems a little high. Perhaps i fcuked the solder joints, maybe dry joint or something. Although, the joint doesn't seem to be getting hot. A lap around the block will confirm this though.