Capacitor discharge ignition problem

[nospam]

My bike was running yesterday, wouldn't start today and after much
investigation it is looking like the ignition module is dead.

It is of course completely encapsulated and damn expensive to replace so I
was looking for a second opinion on what I observed.

The unit is by Kokusan Denki, it has one output to the ignition coil, the
other side of the coil is grounded.

I lashed it up on the bench with a coil.

On applying power it draws little current and sits there 'ticking' at 20 or
30 Hz, it did that on the bike but I don't know if it always used to.

I looked at the drive to the coil with a scope and the 'ticks' are actually
driving about a volt across the coil for about 200us. The coil is about 1.5
ohms.

Doesn't look right to me.

I tried powering it with the coil disconnected and I could hear the
inverter, err, 'inverting' at some high frequency, the voltage on the coil
drive output went negative and quickly past full scale on the 1kV range of
my meter.

Seems to me the pass element (SCR or whatever they use) has gone short
circuit. So with the coil connected it is just current limiting or
something trying to charge up the coil. With the coil disconnected I am
seeing the capacitor voltage on the coil output, but, at over 1kV it seems
rather high. Maybe the inverter has lost regulation and the excessive
voltage killed the pass element? Anyone know if 1kV + is normal for a CDi
unit?

Does anyone think the unit isn't dead?

 

[Jamie]

My bike was running yesterday, wouldn't start today and after much
investigation it is looking like the ignition module is dead.

It is of course completely encapsulated and damn expensive to replace so I
was looking for a second opinion on what I observed.

The unit is by Kokusan Denki, it has one output to the ignition coil, the
other side of the coil is grounded.

I lashed it up on the bench with a coil.

On applying power it draws little current and sits there 'ticking' at 20 or
30 Hz, it did that on the bike but I don't know if it always used to.

I looked at the drive to the coil with a scope and the 'ticks' are actually
driving about a volt across the coil for about 200us. The coil is about 1.5
ohms.

Doesn't look right to me.

I tried powering it with the coil disconnected and I could hear the
inverter, err, 'inverting' at some high frequency, the voltage on the coil
drive output went negative and quickly past full scale on the 1kV range of
my meter.

Seems to me the pass element (SCR or whatever they use) has gone short
circuit. So with the coil connected it is just current limiting or
something trying to charge up the coil. With the coil disconnected I am
seeing the capacitor voltage on the coil output, but, at over 1kV it seems
rather high. Maybe the inverter has lost regulation and the excessive
voltage killed the pass element? Anyone know if 1kV + is normal for a CDi
unit?

Does anyone think the unit isn't dead?

before you deside its the mod, try putting a plug on the coil.
and then just power up the - + with a batter for a .5 or so to
see if your getting any form of spark on the plug.
1.5 ohms seems low to me.
but i could be wrong..