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Virago XV 125 CDI Unit repair


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Hi Guys,

I have recently had problems with my XV 125 and through the help of this forum and a lot of testing with a multimeter i have finally solved my issue.

Turns out that the CDI unit was faulty and i have repaired it now and i thought it would be a good idea to get it up on the forum for future use.

The problem i had was that only 1 cylinder was firing. I only had the front cylinder firing on my bike.

I did the usual, checked plugs, checked coils and all seemed ok. So from there i worked from the Iginition electrical diagram CDI.jpg

If you look on the diagram the command to fire comes from a number of factors:

A = Primary pick up coil

B = Battery

C = Side Stand Switch

E = Main ignition switch

Now remember my bike was only firing on 1 cylinder. So from the diagram i could tell that the side switch was working ok, igintion was fine and the bike only has 1 pick up coil, so if the CDI unit was getting the message to fire then both cylinders should get it.

My rear cylinder was not firing so from the tracing of wiring using the XV 250 service manual i was able to work out the key for each of the connectors for the CDI unit. Coilwithkey.jpg

Now the front cylinder is fed via the orange wire and the grey feeds the rear cylinder.

Just to check i swapped the orange and grey wires on the coils and then it begain to fire. So i knew that the CDI unit was not sending the fire signal to the second coil via the grey wire.

Time to open up the CDI unit!!!

Now opening the unit is not an easy task, the whole board slides into the case and is glued in place during manufacture. So getting this out was not easy but with some (convincing!!) it finally came out. DSCF0824.jpg

I now have the CDI circuit board out of the case. DSCF0823.jpg

As you can see there is not a lot of components to a CDI unit. (which begs the question why does Yamaha want £450 for a new one!!!)

In the electrical diagram components J and K are the power transisters that send the charge to the coils. CDIwithDiodes.jpg

With a short electrical test on these transisters i found that one was not working. In the picture the left hand transister feeds the orange (front) coil and the right hand one feeds the Grey (rear) coil.

It was the right hand transister that was not working. This unit as a 2SD2141 Avalance Diode. See datasheet http://www.classiccmp.org/rtellason/transdata/2sd2141.pdf

This diode is the ignitor, driver for the circuit. So i needed to replace this unit. I managed to find one from a company in Surrey called littlediode.com http://www.littlediode.com/components/search.php?mode=search&simple_search=Y&posted_data%5Bby_title%5D=Y&posted_data%5Bby_shortdescr%5D=Y&posted_data%5Bby_fulldescr%5D=Y&posted_data%5Bby_sku%5D=Y&posted_data%5Bincluding%5D=all&substring=2SD2141&search_redirect=Y

This cost £6.99 with additional £3.00 for first class postage.

Soldered the new unit in, tested and then put the unit back together again. (did have to removed glue from circuit board on edge and from case)

Got it back together, put back on the bike and hooray!!!!!!

Now have bike firing on both cylinders!!!!

So my advice is, before you think about replacing your CDI / TCI unit, take a look inside. You never know you maybe able to fix it!!!

Some websites i found refer to the unit as a TCI and some as a CDI. For more info on this check out this great website http://www.jetav8r.com/Vision/IgnitionFAQ.html

Helped me a lot.

My information here is based on my personal experience with the specific problem i had with my bike. Not sure how it may help if you have other symptoms but i thought it would be useful to put up on the forum for future reference.

Any questions please let me know.

Hope it helps

Dan

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..........................As you can see there is not a lot of components to a CDI unit. (which begs the question why does Yamaha want £450 for a new one!!!)......

Because they are money grabbing barstewards!

Very good write up by the way.

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Thanks bro, am gonna get your info into a PDF...That helps millions mate! B)

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Reminds me of when I used to service disco gear.......lights stopped flashing change the triacs in the lighting controller. In this case a driver transistor.

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Hi

Great bit of info there and bookmarking should this happen to me! Where was the ignition wiring diagram from? I have a Sachs Roadster 125 which shares the XV engine, it's playing up at the moment and some comprehensive diagrams like that would come in handy.. thanks

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Hi

Great bit of info there and bookmarking should this happen to me! Where was the ignition wiring diagram from? I have a Sachs Roadster 125 which shares the XV engine, it's playing up at the moment and some comprehensive diagrams like that would come in handy.. thanks

The diagram is in the XV250 manual mate..cheers! ;)

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  • 9 years later...

Hi,

I came across with slightly similar problem with my xv250TCI unit. My bike rear cylinder is firing but its firing after TDC and also slight misfiring is occur.
I have changed the power transistor's but problem not solved. I think there is either problem with CPU or  Amplification circuit (J) as per block diagram. can you help me to find which component is responsible for delay in firing the rear cylinder.

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