'87 CDI Repair
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Thread: '87 CDI Repair

  1. #1
    Junior Member radbuggy's Avatar
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    Jul 2013
    Boise, Idaho

    '87 CDI Repair

    Long story really short, did "EVERYTHING" to include putting the cdi in the freezer(which helped).
    Cut cdi case in half with a hack saw and pealed the potting compound off the circuit board.
    Using a magnifying glass I found 4 bad solder joints and 7 more needing touched up inside the cdi.
    Lets see if i make it home from work today.




    I can explain more later. If anyone is interested.

    Here is my full story.

    Three years ago my TW200 started to spit and sputter at any throttle position above idle. I got frustrated to the point where I parked it and let life with 4 kids and a wife take over.

    I decided that I would spend my birthday this year getting the beast back on the road. For the past three weeks I have been tinkering with it and learning a few things along the way about TWs. I started by doing a few things to it before I tried cranking her over.
    Cleaned tank
    Cleaned Carb and replaced float needle valve
    Cleaned black soot off spark plug DR8ES
    Cleaned and oil air filter
    Change oil
    Replaced battery
    Washed it
    Change air in the tires

    The little beast fired right up and I was able to ride it around the neighborhood. I was happy for the moment. I noticed that at around 50 mph there was a pulsation and only got worse if I tried to go any faster. I wasn’t too worried about it and I figured it would get me to work Monday morning. WRONG!
    Started it in the morning and let it idle for 3-5 minutes, jumped on and bumped the throttle and she fell flat on her face, spitting and sputtering with any throttle input. &$#%@$(@)^#!. Parked it and drove the truck to work. When I go home after work I jumped on the bike and it fired right up with no issues other than the 50 mph mentioned earlier. I rode it around like this for about a week tinkering with different spark plug heat ranges and gaps, timing light on plug wire checking firing consistency.

    With no issues raising their ugly head I attempted to ride it to work once again. Started her up, let it warm up, jumped on and took off from the driveway, when I was 100 yards from home, !*&^^%#%!($^@!#. Back home it goes. Let the real troubleshooting begin.

    These are the things that I checked or double checked.
    Cleaned Carb bowl, nothing found
    Main jet 114, No shims under needle, Idle/Air 2 ¼, should be lean
    Float level, 1/16 below bowl rim
    Spark plug (still black soot) replaced with new D7ES
    Inspected all ignition electrical connections, no issues found
    Removed air filter element (to see if this clears running rich)
    Put CDI in freezer for 2 hours, then reinstalled
    Started the bike (no choke still)
    Throttle response is good

    Test ride = Hold on to the bars! Noticeable more power and goes 65 mph before she starts to flutter, but now has a small midrange surge (lean condition?).

    One more time to try and let this thing get me to work. Started in the morning, great throttle response, jumped on and away I went. It felt good to finally be riding it in the morning commute, up until I was 300 yards from my work place. ^[email protected]&(*)($^@). It would not do anything but idle AGAIN!

    I proceed to remove the CDI and determined to fix this problem.

    I took a hacksaw and cut, just barely, though the plastic case around the outside edge centered between the top and bottom.
    Using a Leatherman and an Exacto Knife I was able to cut the potting compound and pry the lower side of the case off. This was very simple and the only fear I had was pushing the Leatherman knife blade down the sides of the lower half. The case half came off with a little prying but not much, a lot of the potting compound with the case half. I then inspected the back of the circuit board and bingo. I soldered up the cold joints, used silicone and a little duct tape to seal things up and hold it together and off to the races (Home that is) I went. Still no air filter installed.

    I would highly recommend performing surgery on your CDI, especially if you intend on buying a new one anyway. On a scale of 1-10 this was an easy 4.

    The bike ran great all the way up to 65 mph before it started to flutter a little bit. When I got home I checked the spark plug and it was no longer black and sooty but rather a nice tan color. I put the filter back in and waited till the next morning to go to work. It ran great until 50 mph where it started surging. I pulled over removed the air filter and she came alive again, 65+ mph with a slight midrange surge.

    I got the CDI fixed and now I need help with my air filter issue.

    I believe that I am jetted as lean as it can go, but runs rich if I install the foam element. The element has be washed/oiled, then washed and even run in the bike dry with the same results. There are no blockages in the intake ducting. I am able to breathe though the foam element, so it seems clear.

    ************************************************** ************************************************** ************

    Well, The CDI lasted for two tanks of gas and then started flaking out again. I took it back apart to find that the silicone that I had used really tarnished all of the solder joints that it came in contact with. There were also more bad solder joints on the small circuit board on the opposite side of the CDI. this time I am not going to seal it up with silicone but just duct tape it together in case I have to rip it apart again.

    I am temped to get one of those $16, 12 volt CDIs of of ebay and see if it works at all and have it for an emergency backup.

    It is running very good now, but I suspect it is still rich, as it starts right up with no choke. i am going to run it another tank and then check the spark plug.
    I am crossing my fingers but this time feels right to me.
    Last edited by radbuggy; 08-14-2013 at 02:02 PM.
    bad luck and Ken like this.

  2. #2
    Senior Member TW-Brian's Avatar
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    Dec 2010
    Pleasanton, CA
    Yes, people are interested.

    Cold solder joints, huh. That would be consistent with the guy who told me that he fixed his 1987 CDI by putting a hose clamp around it.

  3. #3
    Member TheRedRider's Avatar
    Join Date
    May 2013
    Menominee, Michigan

    1987 tw


    Wow, good job! I half heartedly tried to milk a few more miles out of my old one this year by putting some force on the harness with duct tape and zip ties. It didn't work. Ended up popping for a new one. My old 87 is back on the road and trails with a new CDI. There are some good threads about aftermarket DC CDI's, wish I knew more about them.
    "keep it punched"

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  5. #4
    Member moresnow's Avatar
    Join Date
    Oct 2012
    Interesting. Let us know if it works. I have a buddy who does a lot of circuit board repair on automotive items that dealerships will tell you are unrepairable. He does it on the side out of his home. He may be a option for somebody without the capability to do this themselves. PM me if you have a non-functioning cdi you would like to have looked at. I could put you in touch.

  6. #5
    Junior Member radbuggy's Avatar
    Join Date
    Jul 2013
    Boise, Idaho
    The CDI is working good. That was quite an easy fix. Wish I would have done it along time ago. It was easier and quicker than rebuilding the carb.
    But I am still running rich. I just drilled about 16, 1/2" holes in the breather box which help a little. New foam filter is on order.

  7. #6
    Senior Member B-dub's Avatar
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    Jul 2011
    Southwest Utah
    Great job on the CDI. It certainly sounds like you've covered the bases. You didn't mention doing the valves, but I don't think that's the problem here. It sounds to me that you've eliminated too little air as the problem. It has to be too much fuel. Any chance the hole in the jet got enlarged while cleaning? It's been done before, and not that hard to do. You might try a new stock size jet. That's worked for a few others. It's also possible you could still be having a timing issue with the CDI. Stick with it and you'll get it figured out. Let us know what you find out.
    bad luck likes this.
    My handle is B-dub, I ride a T-dub, and drive a V-dub.

  8. #7
    Senior Member elime's Avatar
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    Jul 2010
    San Jose, CA
    Thank you very much for sharing your experience. Things like this really help and save $$$$$.

    As B-Dub stated, a new stock jet can work wonders. I replaced my #114 jet with a new one and my overly rich running condition went away. The hole in the center corrodes and though it looks normal it is to big and runs rich.
    bad luck likes this.
    Long live the internal combustion engine!

  9. #8
    Senior Member slowmod's Avatar
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    Apr 2014
    nova scotia
    i'm about to put mine under the knife in the next few minutes. spent the last 3 days trying to get my bike running again after a couple years. went thru everything else, had to be the cdi. did the freezer trick and the bike purred. nice sound.

    i've fixed an intermitttant wiper module with cold solder joints. nice to find this thread with someone who actually did this module and it worked! i'll be looking into an aftermarket cdi as backup, or firstup depending on how tonight goes.

  10. #9
    Senior Member slowmod's Avatar
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    Apr 2014
    nova scotia
    well, i did not find any bad solder joints, they all looked top notch, which is reassuring,

    but... 4 x transistors got ripped from the boards when pealing off the very aggressive anti-vibe rubber layer they are overlaid with.

    so, it's decisive, anyway. i guess i am about to enter the wonderfull world of aftermarket cdi units, and compatability theroff. i will price a new stock unit but i am assuming they are dear.

    i guess the trick with aftermarket compatability is
    a) it's a non-12v system (one could use a 12v and just use the hall sender for the trigger, but naw..), and thus
    b) finding a unit that will work off the charge coil plus the hall sender.

    i found the cdi case disassembly hard; the case is tapered so it doesn't hold in the vice well, and the plastics were bonded really strong. it was difficult not to apply force in the wrong place when bracing against cuts and prys, especially once one side was exposed. i used a hacksaw, boxcutter, vice, and a thin pry bar. i would avise to cut the hard plastic shell into many sections first, then start peeling. on mine, as soon as one cut past the shell the rubber gave blue chips.

    my bike is a '90.

    maybe if i had boiled it in gasoline it would have dissolved the rubber and left the electronics intact....

    here is a photo of a couple of the transistor pulls.

    cdi ripped.jpg

    both the transistors were embedded flush into the rubber at left. i just pried one out.

    the symptoms of the cdi being bad were very carburator-ish. wouldn't take the throttle, surging, backfiring ("lean condition"), start then peter out (fuel supply, vacume issues..), idle barely but with a weird putputput. needed lots of choke.

    some usefull outcomes of this is that i understand the carb and wiring way better now!, i found and fixed the leaking carb-engine flange.

    also, i installed little disconnects on the blue/yellow and blue wires at the cdi connector.
    now, when troubleshooting, disconnect both, and the blk/w connector.
    connect the blue/yellow to ground (i dropped a connector nearby) and the ignition is "on" and totally stand-alone.

    to stop the engine you have to stall or starve or choke it, (or, with one hand, reconnect the blk/w so the kill switch works, while holding the vibrating bike upright). so best to leave that one hooked up maybe. but yeah, now it's easy to just drop out all that interlock shit to help isolate where an issue is.
    Last edited by slowmod; 05-11-2014 at 09:14 PM.

  11. #10
    Junior Member 1984trx200's Avatar
    Join Date
    Sep 2013
    Is the OEM replacement CDI for the '87 just as prone to failure? In other words, has anyone bought a new OEM CDI and had it fail?
    1987 TW200
    1987 TT225 (2)
    1988 YSR50

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