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CDI units how easily do they break


Annaz

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The Srad trackbike project is now at a standstill and all because there's no spark dammit.

I've consulted the wiring diagram :pb2: traced wires all over, checked, voltage tested and even taken the race loom off and tried the original and everything is fine, turning over etc, but no spark.

I am now begining to think the CDI unit is a fault, when the bike was dropped the rear subframe got a hefty clout, enough to bend it out by 10 degrees or so. So the question is how robust are these little blighters, I've seen inside one and it looked like a computer circuit board, which I suppose is exactly what it is.

Your thoughts please, I'm sure there's one or two of you who've dropped them in the past eh?

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Dunno how easy they are to break, but there is one ending in under an hour on eblag (linky). No bids, £20, and 55 minutes to go? Worth a punt I reckon.

It's different to mine, mine is carb model, thanks all the same tho fella.

Will be on the bay searching tonight!

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They're more reliable than ever, but its not unheard of for them to break

70's CDI's - almost guaranteed (I had 2 X7 cdi's burn out)

80's more often than not (KMX200 CDI failed)

90's - not unheard of (TDM850 failed - not mine)

2000's - you'd be unlucky to have a faulty one, but it happens (DRZ400 faulty - not mine but I witnessed it)

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As you've not answered...

If you've got rid of the key operated ignition switch did you remember/know about the parallel +ve feed to the Cdi with the resistor in it?

If you look at your schematic you will see that there are 2 +ve feeds to the Cdi that run through the key switch? One of these has a resistor in series, that is within the ignition switch, and acts as an anti hot wire security device. It isn't shown on the schematic is it is within the ignition switch.

If you have replaced the key switch with a toggle switch and not put the correct value resistor (100 ohm AFAIK) in the correct +ve feed to the Cdi the engine will turn over all day long but will never give a spark.

I think - and don't quote me on this - that when you look at the back of the larger plug on the Cdi (yours may have 2 or 3 plugs - the rectangular main 8? way and a square 4 way to the fuel pump and possibly a round 4 way to the tps?) that the +ve feed with the resistor in it is the lowest left most pin.

The resistor is fitted to all kwak and suzuki ignition switches. Race Cdi's do away with this to make things easier.

Sorry for not answering but I didn't activate the email thingy :thumbsup:

I've read the above with great interest and it seems you could be on to something there as the race harness didn't come with a CDI (so I don't know what system it was running) and yesterday I put the original harness on and guess what? I removed the ig barrel coz the key was snapped in it, and hotwired it instead. So if what you say is true, which I don't doubt, I've got resistor trouble, which is a fucker coz I ordered another CDI last night DOH!

I'm off in the shed to wire the keyswitch up and remove the key, I think I've got a spare somewhere.

I'll let you know what happens!

Thanks

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Update;

Big thanks to Millemille! there is a cunning resistor at the botoom if the ignition switch. I've also found out (coz it still wouldn't spark) that the CDI was cattle trucked, I put another one on and BINGO! big fat sparking antics Hooray!

Only thing to figure now is how to wire the resistor in. It goes from the black/white neg feed (that goes to the - batt terminal) to a copper contact on the ignition switch, but where it goes from there I've no idea. I think a dose of trail and error is on the horizon :eusa_think:

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Update;

I think a dose of trail and error is on the horizon :eusa_whistle:

that could get expensive!

haven't you got a wiring diagram?

if not, try here: http://www.thesparesnetwork.co.uk/forums/v...6a41ea27718ee6f

don't know if there is one there, but a handy place to know, nonetheless

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If you look at your wiring diagram you will see that there are 2 feeds that go to the CDi through the ignition switch - one has the resistor in and one doesn't. the wiring diagram will tell you the wire colours at the Cdi plug so it's a simple matter of taking a multimeter set to measure resistance and measuring, with the key ignition switch plugged in and switched 'on' and the Cdi unplugged, the resistance between the battery -ve lead and either of the the two wires to the Cdi.

One will be very low resistance (the one without the rsistor) and one will be around 100ohms - the one at 100ohm is the one with the resistor in. The resistor can go anywhere between the battery and the cdi...

I spent most of yesterday and most of this afternoon messing with wires. The resistor goes from the secondary orange live feed to the neg, so I unsoldered it and put it in further back down the loom. I've tested it and it was running as sweet as a nut. I kept testing as I stripped away the unwanted bits of wire, like lights, horn etc. Everything ok!

So I taped it all up and now it won't spark again. COCK! Looks like I got me an intermittent fault somewhere, Yippee.

So tomorow night I'll be undoing the tape and starting again. I love bikes me :eusa_whistle:

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Another update;

When I bought the race harness the guy accidentally sent me two other harnesses by mistake which turns out to be a stroke of luck coz I put one of them on and Bingo (take 2!) so I now assume a dodgeyness in the old one. So it's back to square uno but this time I'm going to make double sure before taping up and routing just in case.

Big thanks to Billysbones for that link. I downloaded the workshop manual, excellent that! Nice one! It's packed with diagnostic stuff and really usefull info that a Haynes jobbie doesn't touch on.

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no problems.

Here to please, not to tease!!

good luck with the rest of the bike.

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