Sparks only from right hand side coil GK73A

[SevenThreeSeven]

...and the two other things that I forget

The other two things are Bipolar Triple-stage Darlington Transistors. There's one for each of the bike's coils (2).

What they do: When the integrated circuitry inside the bike's CDI box decides it's the proper time to to "dwell" the coil (charging it up in preparation to fire the spark plug for either cylinders 1&4 or cylinders 2&3) it will send a signal to one of these transistors telling it to provide a path-to-ground for the 12 volt power that is always resting on the coil's primary winding (12 volt power is provided to the coils whenever the bike's key is switched to "on").

The CDI box commands this path-to-ground for about 2.8 milliseconds which is long enough to fully excite the electrical field in the coil's primary winding. Then the CDI box commands the transistor to interrupt the path-to-ground for this power. This causes the electrical field in the primary winding to collapse which causes an exponentially larger electrical field collapse in the coil's secondary winding which grounds out through the High Tension lead to the spark plug, then across the spark plug gap and into the metal of the cylinder head.

The field collapse in the coil's primary winding is a much smaller event than the huge electrical storm of a collapse that occurs in the coil's secondary winding but it still has to be dealt with and that's the most important function of the Darlington Transistor. It catches and grounds the electrical backlash that comes raging back down the CDI's coil control wire as a result of the coil's primary field collapse, preventing it from disrupting and/or frying the CDI's integrated circuitry.

[minkathecat]

i have tried fixing the cdis with my electrical instrument brother in law alas even when fitting the new cappasitors etc it was no go.
NOW DONT FORGET IF SOMEONE OFFERS YOU A CDI PRE 93 THINK IT IS WILL NOT WORK UNLESS THE BIKE IS PRE 93 ENGINE THAT IS BECAUSE THE SPRAG CLUTCH CHANGED AND WILL ONLY WORK WITH THE CORRECT YEAR
YOU CAN FIT HIGH LIFT CAMS OUT THE EARLIER ENGINE STAY WITH THE SAME CDI AND SPRAG CLUTCH BUT YOU CANT MIX AND MATCH THAT CDI AND SPRAG.
SEE SPECIFICATION ON HERE WHEN THE BHP WAS CHANGED.
IF YOU FIT HIGH LIFT CAMS YOU HAVE TO CHANGE PILOTS AND MAIN JETS ALSO DEPENDING ON WHAT AIR BOX SUPPLY YOU HAVE
BEEN THEIR DONE THAT BOUGHT THE T SHIRT.
CDI BOXES ON ALIBABA SITE BUT BEWARE OF IMPORT TAXES
IM STILL SUSPECTING ITS YOUR WIRING HAVE YOU CHECKED FROM CDI TO COIL IS LIVE AND NOT DROPPING CURRENT IN THAT WIRE.
HAVE YOU CHECKED THOSE COIL RESISTANCES (AND LEFT THE METER ON (THIS WAS MY PROBLEM)
HAVE YOU CHECKED PROP STAND WIRING RIGHT UP TO WHERE IT GOES INTO CDI FOR CONTINUITY
REGARDS JOHN

[jamesgoodfella]

So it's looking like I've got a dead CDI, will give it a final check tonight though.
My CDI has "32900 32c00"
Only found one with the same part number on eBay but that one looks like it has different connections.
Can anyone advise on what I should do about a replacement CDI?

[SevenThreeSeven]

It depends on the CDI box. Inside some models of the CDI box there's just a circuit board with easy to replace components, something that a guy with electronics knowledge and skills can easily fix. As mentioned in an earlier post on this thread, these GSXR or Bandit 400 CDIs only have two components that fail: either the capacitors or the ignition control transistors. Once a guy with skills has the CDI box opened up it's a very simple process to replace these items.

The bad side is that some of the CDI boxes where back-filled with a resin foam (for durability, I think). I don't know which versions or bike year-models had the foam filled CDI boxes. This foam makes doing repairs on the CDI circuit board components either more difficult or nearly impossible (not sure which) because a solvent would have to be used to remove it before any repairs could be made.

You should Google TTR Ignition, they have experience repairing CDI boxes.

[jamesgoodfella]

Ordered a CDI with the same part numbers so fingers crossed I can spark up

[jamesgoodfella]

She lives!!.. Well sparks correctly.
Need to finish rebuilding the carbs and I can take her for a spin, any tips on rebuilding and tuning the carbs? Ive fitted the new parts from Litetech.