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Japanese POS! - CBR250RR Electrical Dramas.

Discussion in 'Technical and Troubleshooting Torque' started by MattyB, Jan 15, 2007.

  1. *Sigh*

    Charlie was right, PISS-OH-SHIIIIT!!

    A few weeks ago my CBR250RR was fuggering up and doing all the usual electrical poo's. We diagnosed it as a faulty Regulator Rectifier.

    So Loz and I replaced the Reg Rec and all was good, but not for long. (note; we noticed the plug for the reg rec was looking fried, but it still fired up when we put the reg rec on).

    Then, it wouldn't start cold, but would start once it was all warm (guessing when cold it didn't have enough charge to make a big enough spark? because the starter still turned strong.).
    Anyway, then the starter started to die down, so I was push starting it everywhere.

    Then it wouldn't idle.

    So I figured the Reg Rec fried the battery and stopped it from charging.

    So I got a new battery.

    2 weeks later (now), it's starting to not want to start in the mornings - it'll almost want to kick over, but just doesn't have enough punch. so i can push start it.
    but then it stalled on me last night twice on a late night food run (excuse for a ride.).

    Ok, so today i pulled the duck tail off to have a look-see and see if anything else is poo'd up.

    The Plug -

    And a fuse I stumbled across, lol.

    I'm too scared to take off the front cowl to check the fuse box, 1) because it was a real mission trying to fit that bastard fibre glass replacement on there when we repaired it, and 2) because i'm scared my whole fuse box will be chockers with melted fuses.

    I'm obviously going to replace the plug and fuse - but i don't want to just do that and hope for the best.

    Anyone in the northern suburbs or somewhere with a multimeter/voltmeter and some electrical experience willing to do a rider a favour? I want to test the Stator, battery, and some wires and what-not.

    Find out if there is an underlying problem apart from these 2 before I replace the plug and fuse and ride it for another week, just to have things fry up again.

    Oh, and for any CBR250RR riders wanting those flash alloy heel guards for the bling factor - shave the left hand one down a bit with a bench grinder to prevent this from happening -
  2. I'm not a bike guru, but a good check of the earths would be a good place to start. A bad earth (or connection somewhere :)) will cause excess heat to build up.

  3. Matty, arm yourself with a cheapo multimeter and follow this electrical fault finding link, very simple stuff don't be put off:


    It will almost certainly be that plug that's giving you a headache! The charging system will have a hard time operating properly with that plug! You can buy new ones at most bike shops, don't skimp when it comes to wiring it up properly (no twisted-together wires here!).

    It should have been replaced with the new reg/rec, along with a new battery at the same time. Isn't hindsight great?! Your new battery should still be okay as it will have stopped overcharging.

    While you're checking the fuses, thoroughly check the wiring (what you can see of it) to see if there's any further damage. Also may pay to check the plug on the cdi (black box), under the pillion seat (i assume).

    Good luck, it won't take much to sort it but it should be done properly, take your time!
  4. That is classic corrosion or dort on teh terminals, causing high resiatances.
    Older Kawasakis are somewhat known for it, I picked up a half volt at the battery when running on my Z just by cleaning all the terminals on teh bike thoroughly.
    I think your problem is still poor connections, which lead to your reg/rec issue in teh first place in my opinion.
    Interestingly, I upgraded my old Z to a 250 RR reg/rectifier for a huge improvement in charging performance.

    Regards, Andrew.
  5. Smaller capacity Hondas from approximately 1989-95 are reknowned for reg-recs that fail regularly, some models more so than others.

    Matty, you're right in assuming that the faulty reg-rec boiled your battery, the burnt plug is a normal symptom of an overcharging unit.

    As said, clean up all the wiring/fuses, inspect carefully, SOLDER the new plug on, and you'll be up and running again in no time.

    All of the usual 250cc import places (dare I name them) should carry new generic reg/rec plugs.

    It's not that the reg-recs are especially bad, just that they have a lot of demand placed on them when asked to supply 13.8v+ over a 16k rpm operating range. Electrics have never been a strong point on early 90's Hondas, unusual for sucha quality-driven manufacturer.
  6. cbr 250 workshop manual,
    has a wiring diagram and a step by step electrical fualt finder with a multimeter section, If u get stuck later on
  7. Well well doesn't this look familiar... Guess the actual problem wasn't quite fixed then... :(
  8. If you substitute the word "connection" for the word "earth" in every instance in the above advice, everyone will be justified in thinking you are a bike guru. ;-)


    Trevor G

  9. Really? Most bike shops can't even supply the right wattage instrument panel globes, leave alone "plugs" in wiring connector.

    You are absolutely right in that it is the plug which is faulty, well, the connectors inside the plug, actually. It's a job for an autoelec, no less.

    The connector with loose, unravelling wires sticking out past the insulation is a classic example of an accident waiting to happen. Unravelled wire can only handle a fraction of the current that it can when properly wound or twisted.

    Any connectors which are loose - you know, they slide in and out, or on and off easily - will overheat because the connection is not good. The overheating increases the resistance and so it gets even hotter until it fries. Same with a dirty connector - WD40 or similar is useful, but so is gently closing the folded ends on a spade terminal that carries any sort of current.

    You might be able to buy a complete wiring loom, or the sections that join to the damaged plugs. Maybe. More likely you will need a pro to do it properly. You can remove the connectors from inside the plastic plug by inserting a jewellers screwdriver (an extremely thin and narrow one) from the wire side, to depress the little tang which holds the connector inside the plug. You should then only use the correct type of terminal to go back in.

    The alternative is to simply use a good quality tag strip (available from Jaycar or D ick Smith) and manually connect each wire. Oh, you have to strip and twist and double the wire over for best contact, too. You can even get tag strips which plug in to each other, to make it easy to pull apart again, but that shouldn't be necessary.

    All the best

    Trevor G