From: gaijin@ale.Japan.Sun.COM (John Little - Nihon Sun Repair Depot)
Newsgroups: rec.motorcycles
Subject: [LONG] Electronic Ignition Fix - Do It Yourself Info.
Date: 29 Jul 92 12:05:55 GMT
Organization: Nihon Sun Microsystems - Atsugi Technical Centre - JAPAN.
NNTP-Posting-Host: ale.japan.sun.com
Summary: Sod it!
Keywords: Seca, Yamaha, Goldfish, Electronic-Ignition, CDI

   A couple of weeks ago I posted a description of a problem I was  having
   with my Seca and which I  suspected was being caused by the  electronic
   ignition (intermittent missing,  rev counter  falls back  to zero  even
   though the engine is still making [lumpy] revs).

   Bob Boardman let me know that his Yamaha box died with exactly the same
   symptoms a while back, so I  thought it might be worth dismembering  my
   box to see if there was anything obviously flakey.

   The box itself is made  by Hitachi.  It's very  easy to get into,  with
   four screws holding on  a plastic cover.   Under the  cover the PCB  is
   mounted solder-side up.  The PCB is held in place by a couple of screws
   -and- by the spade connectors which are integral to the molded  plastic
   box (you need to de-solder the spade connectors from the PCB to get  it
   out of the box).

   I decided to remove the PCB from the box for a look-see, but if  you're
   planning exploratory surgery on -your- box I'd advise against this step
   (read on).  The component  side of the board  is covered with a  fairly
   thick layer  of gluey  gunk (kinda'  like potting  compound), which  is
   pretty much what you'd expect for something electronic in an automotive
   environment.  That means that it's fairly difficult to get to component
   legs with meter probes  and pretty much impossible  to read values  off
   resistors, etc.   But it also  means that you  can de-solder  component
   legs without having  the components  drop out,  which is  why I  advise
   anyone else not to bother removing the PCB.

   The layer of varnish on the solder-side of the board makes it difficult
   to check visually for dry joints,  but my guess was that vibration  and
   aging solder were ganging up  to cause just this  type of problem.   My
   action-plan  was  to  re-solder  all  the  joints  regardless   (really
   technical, huh!?!), but this was made  difficult because of all of  the
   gunk on the board.  A stiff wire brush is a good ally for this job!  In
   the end  I  decided  to  de-solder  each  joint  before  attempting  to
   re-solder, as  without  the  de-soldering step  the  contaminants  were
   boiling in the new, molten solder and causing it to bubble.

   De-soldering and re-soldering is  tedious, but not  difficult.  I  used
   one of the butane-gas powered portable  irons and did the job  outside.
   I suspect that the smoke from  the burning varnish and goo is  probably
   as lethal as a guiness-fart (maybe it won't kill you, but it doesn't do
   you, your canary or your underpants any good at all!).

   Anyway, the bottom  line is that  the bike  has been in  use every  day
   since I  did the  work and  it hasn't  hiccoughed once  (as opposed  to
   choking itself for  a few  seconds virtually  every ride  before).   It
   looks (fingers firmly crossed here) as though it's fixed, so if  you're
   comfortable with the use of a soldering iron, I'd definitely  recommend
   trying  this  course  of  action   rather  than  shelling  for  a   new
   "black-box".

-- 
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  | John Little  - gaijin@Japan.Sun.COM  - Sun Microsystems. Atsugi, Japan | 
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