Might it be something as simple as the vacuum hoses from the inlet manifold to the Digiplex?

Ten points for enthusiasm?

......I know, I know.....back of the classroom....

Hi,
No,Ive hit the wall. All of the components check out,voltages are equal front and rear cylinder, resistance values of the coils and triggers match.Ive replaced triggers. Ive tested and checked wiring and even jumped around the wiring harness to no avail. I tried a new coil today and it did not help. Charging system is working normally and there are no issues in the stator or wiring in that system. Ive cleaned connectors in the system as well. Ive tried 3 CDI Boxes and got a stronger spark but it still drops out above idle. Ive inspected the flywheel for any signs of damage that might interrupt a good signal from the triggers and no damage was found. I replaced the battery along the way and added grounds.......Nothing. <sigh>

Did you try to switch colis (vertical to orizontal)?
Did tou try to switch kokusan boxes?
This will allow you to find where the problem is and it will take you just some minute.

Nicola, did you read this topic ?

Maybe its time to check the crankshaft runout ?
Wooddruff keys ?
valve timing and clearances, burnt valve ? Worn guides ?
broken piston ring..........


fuel contamination of the oil ?

Seems like you have covered the electrical issues

Just seems odd that replacing the pickup got you spark but only at idle


so if you have some spark and the fuel is OK time to check mechanical possibilities

To get us all back on the same page, when you say the spark drops above idle. Is this by using a timing light? And you said you bypassed the bike wiring harness. Did you only do that for voltage for the coil and CDI. What about the wire from the trigger to the CDI and on to the coil?

I was also wondering, does the spark only get weaker or is it completely gone and what resistance did your pick-ups measure?

Hi,
The Pick-up coils measure 99 and 99.4 ohms. the lost spark is observed by an inductive timing light and verified by a spark plug. Ive checked the flywheel and the crank there is no issues found with them. It is truely bizarre.

Hi,
When i bypassed the wiring harness, it was on Voltage, Ground and CDI to coil triger wires.

I`m still with the pick-ups as nothing else explains the symptoms.
Meanwhile I would put my money on cable break somewhere where the wires of the pick-ups pass the engine cover (which is not uncommon). If a wire is broken either completely but still having contact or only holding together by a few strands you will still measure a correct pick-up resistance. A low voltage spark will still go through to the CDI unit letting it create a ground signal to the coil but at higher rpm the CDI unit could become "blind" due to an indistinct signal. (I have never heard of cold soldering joints at the pick-ups so I`m excluding that)

G.