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Honda CBR250RR Rectifier/Regulator Exploded...

Discussion in 'Technical and Troubleshooting Torque' at netrider.net.au started by toast, Jun 28, 2008.

  1. Yep, it was one of those 'oh sh.it' moments when I got to have a look at it:



    Didn't hear it go, was riding when the bike just lost all power and I had to pull over. It took out the main fuse, too.

    This unit is only five months old and, according to one mechanic, the make has a reputation for blowing. Apparently for an extra $30 ($180 AUD) you can get one of the Japanese models (this exploded one is from Taiwan) which have fins and are much more reliable.

    This one is actually for the CBR600s... but is apparently fine to use in the little blades.

  2. No it isn't, it blew up in just a few months which means it overheated too regularly, may be fine to use but maybe not appropriate for your model dude to fairing design etc.
    the one with extra fins may solve the problem but you should also check the wiring for any scoring since it blew your fuse as well.
  3. I have been riding with high-beam on during the day and night, only turning off when sitting at lights. I was wondering if this on/off of high-beam might be causing it to overheat. Either that, or just using high constantly. Although, I have been assured that a well manufactured rec/reg is designed to handle high beam okay.

    My mechanic pulled this one out and replaced it with a temporary unit from one of his spare bikes - until I take this one back to the guys that put it in to get it replaced under warranty.

    This one also had a lot of thermal paste between it and the metal backing plate. I think it might have contributed to overheating because thermal paste is only to be used sparingly, to fill any air cavities where the metals don't touch. If the paste is also in between the contacting metals, heat doesn't transfer so well.

    Thermal contact conductance of: Air < Thermal Paste < Metal-to-Metal contact.

    I think they (the honda repair shop that originally put it in) will just replace this with another. I am tempted to say no, please put in the finned one and I will pay the difference.

    If they complain about this unit blowing, I will point out that they were supposed to stop this from happening again (ie, fix the problem). This unit and a new battery was put in five months ago after the bike went dead approximately three or four months after I purchased it. They had to check through all the electrics to isolate the problem and that was their chance to make sure nothing was causing the unit to fail.

    When I asked them what caused it to go (the first unit), they said they did not know, but that the unit had not been mounted on a metal backing plate. These guys are supposed to know what they're doing, so the onus is on them, at least from my point of view.
  4. Not quite sure what you mean by some of what you wrote about thermal paste.

    It is designed to transfer heat between a heatsink and the object it is meant to be cooling. Only enough TP should be used to cover the contact area, and none (=NONE) should smear over the edges.

    TP is electrically conductive as well, and from time to time we see the results of clowns trying to fix their own computers using so much paste that it droops over the side of the processor and contacts the pins. The CPU then dies... :-(

    Too much paste can reduce the amount of air flow between the two objects, and around the critical contact area of your Reg-Rect.

    Water is bad for them also - I killed 2 Kwacka ones years ago by spraying water injudiciously around the reg-rec area. It would pool on top of the device and become conductive - the clue would be a nice head of steam rising from under the sidecover!

    Sounds like a good idea.


    Trevor G
  5. If two bodies of metals can contact each other perfectly, there is no need for thermal paste, as the metals' thermal conductance is far greater than that of paste.

    Thermal paste is only required because most bodies do not contact each other perfectly and surface imperfections cause air gaps. As air does not conduct heat very well the use of paste is required.

    I would always mount very fine wet/dry sandpaper on glass and flatten the surface of my CPU heatsinks to a higher degree of accuracy so that they would mate better with the CPU. A twisting motion generally ensured the correct finish was achieved. Less paste was required as a result and a higher overclock could be reached.

    Some pastes had silver added to them to improve their thermal conductance, such as Arctic Silver.
  6. That's better. At least you know what you are talking about. Just apply the same rules to the reg/rec if TP is used.


    Trevor G

    PS And one with a heatsink will always run cooler, all other things being equal.

    PPS You shouldn't use high beam in daylight against on-coming cars - it's a very annoying distraction.

    You just need to be seen, not seen as a nuisance. ;-)
  7. Try one from a pre '99 R1.
  8. The baby's high beam is pretty damn weak (and only one of the two lights is active), which is why I use high-beam. Normally people will flash if your lights are too bright, but no one does. I've been careful to make sure it isn't going to be a problemat night. They are just like a car's standard beam which is a little stronger than normal.

    I've thought a lot about it and concluded that it is better to be a little bright than not be seen and get taken out. If I was riding a new bike, I would not use high beam.

    Honda's decision to use a single headlight for standard beam is puzzling, considering that two lights can be picked out from background lights easier than a single, which tends to get lost.

    Motorists instinctively look for two lights (even if they are spaced further apart).
  9. So you reg/rec is toast perhaps?

    I wouldn't be too worried about thermal paste or anything there. The cbr250 is famous for destroying reg/recs, that being said, if it's cooked like that, i would be looking for other causes. Eg: Corroded wiring, bad earth, etc.

    Lets put it this way, my reg/rec hasn't blown and it's not mounted in the metal plate, as the Tyga kit relocated it to under the fuel tank on two bolts.

  10. Thanks, dis. I'll be sure to ask the honda people to check the wiring out. Although, they supposedly checked the wiring after the last one died... They want to see the bike and my receipt before sending it off for a warranty replacement. Will get to the bottom of it without a problem because they have a good reputation.
  11. I had some issues with my cibbie, which turned out to be excessive resistance in the starter solenoid. This was causing fuses to literally melt, it damaged wiring, and I think was causing the reg/rec to work overtime to regulate the voltage.

    I believe the previous owner had problems with wiring melting and batteries going flat, and i guess never found the cause of the problem. He replaced the reg/rec. (Bike belonged to mattyb)

    Not suggesting that this is the fault you have, but just that it could be any number of things.
  12. Cheers, dis. I'll keep that in mind.