Author Topic: Weak spark : Blame the CDI or not (Read 6006 times)

kardinalios · « **on:** April 16, 2005, 01:04:22 PM »

Hi there. 2 months ago my 92-Bandit 400 begun to have some problems with charging system (battery run out after 2-3 days) and i decide to change the regulator-rectifier with a new one (OEM). The problem solved temporarily (for 2 weeks) and suddenly one day i had a total electrical black-out. Of course battery was dead. I replaced with a new one and tried to start it but since then i couldn't. After few checks i noticed that i had weak spark at the plugs. I replaced with four new but the situation wasn't improved. All the "candidates" for mailfunction (signal generator, alternator, battery, rectifier, cables) are ok according to service manual checks. The only outlier is the low resistance of the secondary of each HT coil (measured 20KOhm).
So i try to measure the voltage that goes from CDI to primary of each coil and i found it about 5 Volts. Since i don't know what is the appropriate value for this voltage does someone know if it is right or wrong.
Of course any other suggestions and solutions to the above problem are welcomed
THNX

Krautwagen · « **Reply #1 on:** April 16, 2005, 08:37:54 PM »

Hmmm. I would troubleshoot your electrical issues before you look at the weak spark issue.

If your generator and your battery are good, but it keeps dying after you charge the battery, chances are you have a drain. Disconnect and charge the battery, hook up the ground and hook up an ammeter inline with the positive. Key off you should see very little current (not sure what exact spec is, but definitely shouldn't be more than 1 amp, a few mA is all thats allowed on cars). If that checks out, you may have a short to ground when the key is on.

Maniac · « **Reply #2 on:** April 17, 2005, 02:16:56 AM »

I'm pretty sure that wire should have 12v on it... but it's pretty hard to actually test, since it's only energized when the igniter thinks the system should be firing.

What is the voltage going into the Igniter?

I'm with Kraut, it sounds like you have a drain somewhere.

kardinalios · « **Reply #3 on:** April 18, 2005, 12:02:02 PM »

Quote from: "Maniac"

I'm pretty sure that wire should have 12v on it... but it's pretty hard to actually test, since it's only energized when the igniter thinks the system should be firing.

What is the voltage going into the Igniter?

I'm with Kraut, it sounds like you have a drain somewhere.

I put the ammeter and it reads about 1-2 mA. Sounds normal.
When you say "voltage going onto ingiter" you mean the primary of HT coil ? I checked it with an oscilloscope and i saw the pulses that CDI sent was about 5 Volt.

Maniac · « **Reply #4 on:** April 18, 2005, 01:44:53 PM »

No, one of the wires going into the Digital Igniter box (your calling it a CDI, which a lot of people do but is incorrect) is a 12v power lead. I -believe- it's the orange/white one, but I'm not 100% sure on that.

kardinalios · « **Reply #5 on:** April 20, 2005, 10:35:36 AM »

You're right. It's the orange/white stripe. I measured also all the others with key on and i had:
Orange/white stripe =12V (from Battery)
White = 12V (1-4 coil)
Black/yellow stripe = 12V (2-3 coil)
Black/blue stripe = 2V (signal generator)
Brown = 2V (signal generator)
Green/yellow stripe = 3.6V (?????????)