AllanA
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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.
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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<source src=”https://photos.google.com/photo/AF1QipNSLLwrUSPpgmy010Qk9kc8JISYU8KAWmfi1O0C” /></video>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.
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.
You could try this. Plenty of WD40 on the rusty fixings and leave it to soak in overnight. Use a hacksaw to cut through the rusty exhaust close to the cylinder head but be careful not to damage the fins. That will provide more room to work on those rusty fixings. The hex head may undo using a ring spanner or socket. If that fails us a good quality mole grips. The Torx will be more difficult but if it won’t undo with a Torx key or socket you may be able to grip it with the mole grips. Drilling it out is another option but if you don’t know what you’re doing you can cause more damage!
Bear in mind that debris is likely to enter the exhaust port so you’re going to have to remove the head and vacuum any debris off the piston crown and out of the port.
Let us know how you get on!
A couple pics of my machine.
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
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.
I’m a little confused here. You say you have cleaned out the carbs and the fuel injectors. Tell us a little more about your bike first, what year, model, carb OR fuel injection, you can’t have both!
Does it actually run or did it run before you carried out any work?
What do you mean by a buzzing sound? Which part of the engine/bike is it coming from?
How did you check the spark plugs?
A bit more detailed info may assist in helping you geting back in the seat again.
Just one further question. Do you have any/much experience of working on a motorcycle?!
:):) I’d love to go for a long ride once I get the bike back on the road BUT the island of Faial is only 65 km around the perimeter with a huge volcano in the middle that takes up lots of landmass! However I have been know to have a day out and ride arounf the island three times to get a couple hundred kms on the clock!
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!
