Another CDI thread
Close
    
    
Results 1 to 8 of 8
  1. #1
    Senior Member Retroben's Avatar
    Join Date
    Aug 2010
    Location
    Southern Oregon
    Posts
    315
    Hey everybody,



    Looks like I chased down the CDI problem. But the process was hard enough I thought I should post it. I used the Wiki as my guide.



    PO said (posted elsewhere on this forum) that he had replaced the CDI box, after which spark went from none to intermittent.



    The plugs are brand new, the right ones and gapped correctly. I installed the battery off my 81 CX500C, and kept it charged up throughout the process. With the plugs still out and grounded to the head (kill switch checked) cranked and observed good spark on cyl #1, weak and intermittent on cyl. #2. Unplugged kill switch circuit at CDI bullet connector (under the seat) and still getting the same behavior.



    Removed CDI box. The back is all melted and looks like it's been dug into already. So the CDI box is now the prime suspect.

    I have a known good CDI box on my 81 CX500. I swapped them...and still got the same behavior!



    At this point I could have saved myself hours if I would have done what I ended up doing after frying multimeters on the HT lead tests.



    Multimeter test showed HT lead #1 gave pretty rhythmic 150s, HT lead #2 gave much lower readings and it jumped up to around 100 only once or twice in 15 seconds(sorry) of cranking. NOW I realize that the multimeter died as I was testing lead #1, so the readings from lead #2 were worthless. Turns out the HT lead test blew out my (mid-priced $19) digital multimeter! Plugged back in to HT lead #1 and even though I SEE a spark it reads zero. Then put it across the battery posts and got 0.4...so I know my multimeter is fried. Had another even cheaper multimeter, and went through the same process and fried it the same way!





    Now I realized, if I have a system that consists of two halves that basically do the same thing, and one half works and the other doesn't, then I can learn a lot by just switching part of the working circuit for part of the faulty one...so I switched the pink and yellow bullet connectors at the CDI box. These are the LT leads to the coils. Gee, #1 still has spark, #2 still does not. The only thing it can be now is the #2 coil. Swapped for a known good one, and



    GOOD SPARK ON BOTH!!



    Still won't start though. Carbs next I guess.
    1982 CM400e As simple as they get
    Fond recent memories: 1980 CX500D 1983 GL650i 79 CX500C '78 CB550K '81 CX500C '82 CB650SC '81 GL500

  2. #2
    Senior Member Reg in Bristol's Avatar
    Join Date
    Aug 2010
    Location
    Bristol-UK
    Posts
    3,631
    You tried to measure voltage on the HT leads?

    no wonder you screwed the meter.

    Pretty sure the wiki test says LT leads OC from the CDI

  3. #3
    Senior Member Retroben's Avatar
    Join Date
    Aug 2010
    Location
    Southern Oregon
    Posts
    315
    Quote Originally Posted by Reg in Bristol View Post
    You tried to measure voltage on the HT leads?

    no wonder you screwed the meter.

    Pretty sure the wiki test says LT leads OC from the CDI
    AAAAAAAARRRGGGGHHHH you are right! Damn I'm glad those multimeters are cheap! And that's why I always shut off the juice before I work on anything electrical. I sometimes wonder how I've survived all these years.
    1982 CM400e As simple as they get
    Fond recent memories: 1980 CX500D 1983 GL650i 79 CX500C '78 CB550K '81 CX500C '82 CB650SC '81 GL500

  4. Remove Advertisements
    CX500Forum.com
    Advertisements
     

  5. #4
    Senior Member Reg in Bristol's Avatar
    Join Date
    Aug 2010
    Location
    Bristol-UK
    Posts
    3,631
    yep, it might have bit you when you were poking around with the probes

    and cranking the engine.

    Oh well, now you know

    Off to the multimeter shop with you young man

  6. #5
    Senior Member Justen's Avatar
    Join Date
    Aug 2011
    Location
    Moorhead, MN
    Posts
    1,725
    It would be easier, or cheaper in 19 multimeter prices to, pull each coil and do a resistance check. If they are close in numbers, they should be good. For cdi test, you test off the cdi. You could test with the pink and yellow wires and can tell if it's a cdi issue. Every so often, you should do a resistance check on the spark caps themselves, if they still have the resistor in them.
    My toys
    1999 Suzuki LS650 Savage
    1997 vulcan


    Wife's toys
    2009 Sportster
    2010 Ultra

  7. #6
    Lord of the scrapyard baldgrimsbybiker's Avatar
    Join Date
    Oct 2010
    Location
    Grimsby - England
    Posts
    717
    Correct me if I am wrong but doesn`t the HT lead kick out something like 30,000 volts or so and not 12 ?

  8. #7
    Senior Member Reg in Bristol's Avatar
    Join Date
    Aug 2010
    Location
    Bristol-UK
    Posts
    3,631
    Yep

    these little meters,

    'they dont like it up em' as Cpl Jones would say

  9. #8
    Senior Member Retroben's Avatar
    Join Date
    Aug 2010
    Location
    Southern Oregon
    Posts
    315
    OK, now my confidence is a little shook. I was sorta hoping the PO's mechanic was wrong and this bike did not need a stator at 15k.



    Being lucky enough to have a running CX did help narrow things down.



    Resistance readings on the CDI connector pins seem to be the same as my daily rider, all well within the ranges in the chart on the Wiki.



    Have swapped known good coils and known good CDI box (off my daily rider). No luck. Yes, kill switch circuit disconnected.

    I can see spark on both cylinders (plugs out and grounded to the head) but not seeing good voltage off the LT leads to the coils. Hmmm.



    Just for giggles I swapped the carbs off my daily rider too (had to plug the petcock vacuum line), you'd think I'd at least get a cough, right? Nope.



    I think the only component I haven't swapped yet is the stator!



    I'm seeing some evidence of water staining and wondering if this bike wasn't in a flood, which could cause corrosion that would kill a stator, no?



    Any more diagnostic guidance would be appreciated. I'm trying to master "methodical" here. Growth experience.
    1982 CM400e As simple as they get
    Fond recent memories: 1980 CX500D 1983 GL650i 79 CX500C '78 CB550K '81 CX500C '82 CB650SC '81 GL500

Sponsored Links

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •  

Similar Threads

  1. Another E-Fan thread . . .
    By JWink in forum Technical Help Forum
    Replies: 9
    Last Post: 06-09-2013, 11:40 AM
  2. Cold oil thread.
    By Blindstitch in forum General Discussion
    Replies: 26
    Last Post: 10-12-2012, 11:53 AM
  3. my shiny thread
    By aaronclark75 in forum Build Threads
    Replies: 23
    Last Post: 05-27-2012, 04:31 PM
  4. Please delete this thread
    By MercedesStenz in forum Selling and Buying Forum
    Replies: 33
    Last Post: 04-22-2012, 05:31 AM

Search tags for this page

why does the back of my cdi box look like it is melted

Click on a term to search for related topics.