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What is a CDI box? Why is mine broken? and how much $$?

Discussion in 'Technical and Troubleshooting Torque' started by dm_obrien, Jun 15, 2006.

  1. Hey,
    Just a quick question, I spoke to the mechanic, apparently my bike has a busted CDI unit. This is news to me, I didn't even know it had a CDI box, or what one is for that matter. But then again, what i don't know about bikes could fill a library.
    Can somone give us an idiots guide as to what a CDI box is, roughly how much a new one will cost (or second hand)? (CB250 by the way, red.)

    I know now its the reason neither of my spark plugs were working, and why it wasn't starting which is good. Hopefully i can get out of this cheap, damn being a poor student. :(

  2. CDI - Capacitive Discharge Ignition. Or more simply the little black box that makes the spark plugs spark when they're supposed to. No idea what one would cost though.
  3. CDI = Capacitor Discharge Ignition.
    Spark plugs are connected to a distributor ... distributor is connected to an ignition coil ... ignition coil is connected to both battery and CDI.
    Basically, the CDI's job is to send an electrical pulse to the coil which the coil then uses (utilising additional battery power) to amplify the electrical pulse and send it to the distributor (which then distributes/cycles it the spark plugs)
    For more detailed/accurate description .. google is your friend :)

    So, if your CDI isn't working then your spark plugs aren't getting any/enough power to generate a spark .. no spark -> no fuel igniting -> no pistons being pushed -> bike doesn't go.

    I reckon a new OEM CDI shouldn't cost any more than $80 ??? and maybe 15mins labour to pull off the old one and attach the new one ??? Maybe $10-$20 for a 2nd hand CDI from the wreckers ???
  4. Well if your handy with the soldering iron there are many designs on the net to build a new one if you are so inclined

    A CDI typically stands for Capacitor Discharge Ignition been about for about 25 years now and is the method for firing the plugs after recieving a signal from the impulse rotor ( hall effect sensor )

    There is a shunt circuit in their make up that does not allow the capacitor to recharge until it is empty from the previous fire

    In a nutshell your CDI has been around for 14 years firing away for all its previous owners and has now given up the ghost just think of all those points that would have been used in that time thats wy they whent that way

    give it a rough guess 100 bucks to 150 bucks should see you on your way again for a second hand unit dont know for a new one though

    Why do they go bang ??????? life expired ???? Been bounced around lately ????? any welding done on the frame ?????? any electrical short circuits ??????? have you been cranking the bike over with the plugs not grounded out on the engine case ????????
  5. All of above. $250 is the most i've heard of new.

    Be warned that a second hand one may let it's smoke out not long after you buy it.

    You can get aftermarket ones for Suzuki, but I don't know about Honda.

    BTW guy, are they really CDI's these day? or do we just call them that? I think I remember reading somewhere that true CDI ignition went by the wayside in the 80's
  6. Iblast i think you are thinking TRI which was about at the same time using transistors CDI is to cheap to make on a line maybe $ 10 bucks if making in bulk probably even cheaper now with surface mount etc the most labour cost is in the wiring harness connections
  7. Thanks for your help guys, this is just another reason why I hate electronics. Good thing I quit that degree.
  8. Cant recommend making it yourself, from what I remember they make it 100% impermeable (and unservicable) by casting it in resin after manufacture. (being a static assembly)

    Pull one off a wrecked bike, shouldn't be too bad, it's most likely gonna be okay if it came off a crashed bike instead of a bike that gave up the ghost.

    Maybe the transistor "wore out" or a connection got work stressed and broke
  9. Update: The new CDI box cost $199, ($325 fitted). Plus the major service the bike needed, Total: $587.95.

    I think I'll just open a joint bank account with the mechanic so he can just help himself as required. I think I'm in the wrong industry. :p
  10. $126 to fit a CDI box? That's normally about a ten minute job. Shop had a glass door didn't it? cos he sure saw you coming.
  11. Yeah, I do wear my noobness on my sleeve. Actually, I think it also included the 'initial diagnosis' of the problem at $82/hr. But I am new to this, and not sure I picked the cheapest or best mechanic. Anyone got an opinion on Northside Team Moto in Brisbane?

    I don't want to sound like a whinging poor person, but I am a whinging poor person.

  12. You definitely didn't pick the cheapest one!

    Diagnosis aside, fitting the cdi is as simple as unplugging the old one and plugging the new one in.