CDI teardown and repair
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Bike Model = : 2008 Hyosung GV650 Carby
I have an issue with my CDI whereby the front cylinder fires properly and the rear cylinder is intermittent or sometimes non existent.
I have done all the usual circuit testing for continuity and good grounds. Battery holds 12.8 volts and 14.4 volts when running. Coils, leads n caps, stator and pickup are all good.
The CDI pinout in the manual provides the relevant resistance between pins and on checking mine I find I have many pins giving high resistence and a few have zero resistance.
So I’ve concluded that the CDI is the problem component and highly likely to be the board solder joints rather that failed components. Solder joints can develop high resistance or open circuits through dry or cracked solder.
My question is has anybody attempted a GV650 CDI repair and if so which way is the board inserted into the casing? Solder joints to the flat side or upper side of the casing?
I have an idea which side to open up but just asking for confirmation purposes.
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That is a unique question and one I am actually keen to learn more as you want to risk opening it up. Normally, I just replace the CDI’s on customer bikes, the lower class 125 & 250ccs don’t even look encourage to try to open them up! as if there was some kind of black goo plastered all over with only connectors showing and that’s it.
If your CDI has plastic casing on both sides (I have to assume so, as i know some 650’s do, but i never actually had my hands on a GV version) , there should be a line going all the way around acting as a seem / seam <?> . Then slowly try to pry it open?
Another overlooked issues we get on bikes is heat fatigue on what it does to electronics , like a computer PC, if an SSD runs too hot without cooling it, it’s circuitry you will see scorch marks on the PCB. Heat is usually a bike’s enemy either to the engine pistons or electronics!
Following this topic!
// Meditation doesn't mean you have to sit still....
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Hi Marcel. Thanks for your response.
Over the last couple of years I’ve split open a few car engine ECU’s and programmed and replaced EEPROMS. So this CDI will be a bit of a challenge but it doesn’t work anyway so really nothing to lose.
Yes, I saw the joint but if I cut along that line it would put me in the middle ground between component side and solder side and leave me with a lot of the potting compound to carefully dig into and remove. So I think I will tackle this by carefully cutting with a mini dremel along the radius of base and sides which I’m reasonably sure will expose the solder side of the pcb.
I’ll post some pics as I progress and see how it goes!
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I made a start on this today having decided where to make the cuts and the fact that my diagnostics on the pinouts showed the CDI is only part functioning anyway with many high resistances so nothing to lose. The Dremel cut through the plastic case like butter so I had to be careful not to go beyond the 2mm thickness of the case as I didn’t want to damage the board or any traces.
Once I’d cut through on three sides I applied some heat from my hot air station and gently slid a flat head screwdriver under the casing and gently probed and lifted until the lid came off. You can see in the pics the rubberised substance that protects the board components from vibration damage. Applying heat softens the substance and using a plastic tip I was able to slowly remove it to expose the board and conponents on that side. It’s mostly clear of the gunk now but nowhere near enough for reflowing the solder joints. Just as a matter of interest I checked continuity between each of the 16 pins and their solder joints on the board and most of them had high resistance which confirms to me that there is a lot of dry/poor solder joints.
I’ll attach some pics at this point and more as the project continues.
Also attached is the results of the pinout tests I did before deciding to open up the CDI.
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https://docs.google.com/spreadsheets/d/1bWOizonguzgNbCebjNoDo78kZ32UH9Q0gQ02I0XPFYo/edit?usp=sharing
RED indicates resistance HIGHER than specification in the manual
Green indicates resistance WITHIN specification in the manual
Blue indicates resistance BELOW specification in the manual
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Looks like Google is saying that we need access , would it be possible to directly upload the photos on to the forum using Add Media button on the reply box.
Also it should allow the document to be uploaded too.
I need to find a toasted CDI from the lower class GV models and see what i can discover , this looks fun to open up 😭😬 , the whole shell is once piece but with lots of black goo underside , if i dremel through the plastic , i may actually cut through a capacitor resting on the walls inside if it has one!
// Meditation doesn't mean you have to sit still....
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Hi Marcel. I can’t seem to find a way to insert media which I have in my Google Photos. Any suggestions would be helpful.
Download the photos to PC / Tablet storage or Phone Storage , then click “Add Media” on this forum to manually add them 🙂
I think it’s time i find an easier way to do it soon while i revamp the site later in the year (time is my enemy!)
// Meditation doesn't mean you have to sit still....
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Well I’m trying that but it just asks me for the source rather than letting me cut n paste or drag the pics into the source box. Any other way I can get them to you? I have some more text to enter too but some pics would help the explanation too.
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The feature was removed a while ago not to drag & paste in to the reply box as a security measure (hence you don’t really see much spam-bots on here, as i was strict), I will find a way to re-introduce it, bare with me on that one.
For the time being, you would have to manually add picture using Add Media => Find the source where it is (eg. in your ECU folder of your phone’s Gallery where you downloaded the google images to ?) , sorry for the hassle! As long as the image is uploaded , it will actually paste it inside the white text reply box for you and you can move them around the words as you see fit.
// Meditation doesn't mean you have to sit still....
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<video controls=”controls” width=”300″ height=”150″>
<source src=”https://photos.google.com/photo/AF1QipNSLLwrUSPpgmy010Qk9kc8JISYU8KAWmfi1O0C” /></video> -
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Hmmm, doesn’t seem to like me!! Oh well, a brief update then instead.
Firstly these igniters on the GV650 are described as CDI’s. They are NOT! As I found out from my tear down.
They are actually transister controlled igniters (TCI) and work just like the old engines that have distributer, points and condenser, except it’s done electronically by a thyristor switching the 12v supply to the ignition coils to ground causing the electromagnet field to collapse across the secondary windings of the coil which in turn creates a spark at the plug. It is a wasted spark configuration for simplicity.
As a tip to others reading this, if you are unsure whether you have TCI or CDI unit a simple confirmation check is to turn on the ignition and use a tester/multimeter between the ignition coil positive terminal and ground. If you have battery voltage (c12V) it’s a TCI if you have no voltage it’s a CDI.
The Kokusan Denki BB7725-1 fitted to the GV650 Carby looks to be multi use with its 16 connecting pins and the same unit is used on the GT650 Carby but utilising some different pins as can be seen when comparing both wiring diagrams. This was done probably as a cost saving design. The pcb uses surface mount technology rather than through the board so replacing components is much more tricky.
I’m thinking at the moment to build my own TCI and have priced up components which amount to c45 euros plus the price of a decent project box to mount it in. The main component would be a Arduino Nano microcontroller which is programmable to ensure correct auto advance of the ignition and dwell adjustment.
The alternative would be to buy a new programmable unit for c200 euros.
I’ll sleep on it for now!!
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I decided today to further split open the plastic case of the unit. It’s unreparable anyway so it’s good to open up and explore the setup. Once I’d opened the casing and removed the rubberised compound a whole range of surface mounted components was exposed, 2 large thyristors which I think are for grounding the two ignition coils, a reasonable size micro-processor which probably control auto advance, dwell and other functions, and a large pickup signal conditioner to smooth out the pickup coil’s AC signal. Additionally a range of capacitors, resistors and transistors.. All in all, confirming that repairing this unit is not for me!!
It appears to be quite a complex two sided pcb with much more than just the basic requirements for a functioning TCI so with this in mind I am going to order the components I need to build my own unit with a programmable microcontroller for timing and dwell control.
It may take a while but I will update the post as I progress.
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