Diminishing output from CDI - 30 Volts to 2 Volts

[DaveC]

check the reg/rectifier

All done in less than 3 pages and countless voltmeter readings

[FlyingBlindOnARocket]

Originally Posted by DaveC

check the reg/rectifier

All done in less than 3 pages and countless voltmeter readings

That's new also... The connector is a good shape and seated.

[carasdad]

The power wire for the CDI does not pass through your regulator/rectifier. The R/R has nothing to with spark. Gradual loss of spark usually points to the pickup coil just above your flywheel. Should be a blue or blue/white wire from your stator. Voltage should be about .5v to 1.0v. An anomaly with the pickup coil is that after a few firings or when they get warm from running...they lose voltage because the coil is faulty or stator voltage to them is irregular or too low.. This means your CDI may not be firing at the proper time i.e. late, at which time some of the current in CDI's capacitor has bled off giving you a weak spark. So get out your multimeter and check the pickup coil voltage.
Glenn

[FlyingBlindOnARocket]

Originally Posted by carasdad

The power wire for the CDI does not pass through your regulator/rectifier. The R/R has nothing to with spark. Gradual loss of spark usually points to the pickup coil just above your flywheel. Should be a blue or blue/white wire from your stator. Voltage should be about .5v to 1.0v. An anomaly with the pickup coil is that after a few firings or when they get warm from running...they lose voltage because the coil is faulty or stator voltage to them is irregular or too low.. This means your CDI may not be firing at the proper time i.e. late, at which time some of the current in CDI's capacitor has bled off giving you a weak spark. So get out your multimeter and check the pickup coil voltage.
Glenn

The pickup coil is new also, and has checked out ok. However, since your description fits the problem I'm having I'd say it was worth another look. Would a few seconds from a cold start (attempt at starting actually...) be enough time for the trigger coil to warm and fail? I haven't kept the starter running for more than 5-6 seconds at a time, and the drop occurs immediately. Also, if I try to start it again immediately afterwards, the power from the CDI doesn't start out at 30Vac, it starts either at 2Vac or slightly above. After sitting for a while (I've never noted how long it takes) then it will return to starting at 30Vac then dropping. That seems to fit in with what your saying if it can happen in that span of time.

[carasdad]

Originally Posted by FlyingBlindOnARocket

The pickup coil is new also, and has checked out ok. However, since your description fits the problem I'm having I'd say it was worth another look. Would a few seconds from a cold start (attempt at starting actually...) be enough time for the trigger coil to warm and fail? I haven't kept the starter running for more than 5-6 seconds at a time, and the drop occurs immediately. Also, if I try to start it again immediately afterwards, the power from the CDI doesn't start out at 30Vac, it starts either at 2Vac or slightly above. After sitting for a while (I've never noted how long it takes) then it will return to starting at 30Vac then dropping. That seems to fit in with what your saying if it can happen in that span of time.

Remember.. a pickup coil is just that..a coil..so anytime current passes through it the resistance from the windings creates a secondary condition besides a magnetic field..that being heat. Heat as you know is an enemy to any type of coil as it reduces its output. Hence the reason Electrical Power Sub Stations have oil cooling or liquid cooling for their transformer coils.
New parts or not..many arrive unserviceable.. I order CDI's for example in lots of 10 from my wholesaler..and always 2-3 of those are dead on arrival. Chinese QC is not like Japanese..German or Italian QC.
Lastly by trade I am not a certified mechanic..but a retired military medic..who later became a cardiac nurse..then gave that up to run a scooter parts/repair shop. It's just me so I get to be my own boss and everybody enjoys working for somebody they really like..lol.. But..anyway..the above is my 2 cents. I see pickup coils fail often and they exhibit exactly what you describe. Lets hope it is a simple as that. Btw..what was the voltage you got from your pickup coil initially..then again after the spark weakened after a few cranks on the engine. If you see a voltage difference before and after that..well you pretty much have all the evidence ya need I would think..
Glenn
P.S. Does the hot wire from the stator to your CDI also drop in voltage after a few cranks? Cause the stator is a coil too..so all the above things that affect a coil..will affect that coil as well..

[FlyingBlindOnARocket]

Originally Posted by carasdad

Remember.. a pickup coil is just that..a coil..so anytime current passes through it the resistance from the windings creates a secondary condition besides a magnetic field..that being heat. Heat as you know is an enemy to any type of coil as it reduces its output. Hence the reason Electrical Power Sub Stations have oil cooling or liquid cooling for their transformer coils.
New parts or not..many arrive unserviceable.. I order CDI's for example in lots of 10 from my wholesaler..and always 2-3 of those are dead on arrival. Chinese QC is not like Japanese..German or Italian QC.
Lastly by trade I am not a certified mechanic..but a retired military medic..who later became a cardiac nurse..then gave that up to run a scooter parts/repair shop. It's just me so I get to be my own boss and everybody enjoys working for somebody they really like..lol.. But..anyway..the above is my 2 cents. I see pickup coils fail often and they exhibit exactly what you describe. Lets hope it is a simple as that. Btw..what was the voltage you got from your pickup coil initially..then again after the spark weakened after a few cranks on the engine. If you see a voltage difference before and after that..well you pretty much have all the evidence ya need I would think..
Glenn
P.S. Does the hot wire from the stator to your CDI also drop in voltage after a few cranks? Cause the stator is a coil too..so all the above things that affect a coil..will affect that coil as well..

So you promoted yourself right on to President and Janitor! I like working for myself, but my boss is a demanding tyrant...
The stator seems fine, it's showing +/- 80Vac consistently measured from the red/black wire at the CDI connector.
I'll have to measure the trigger tomorrow, I hadn't thought to check it in comparison to the CDI output. I don't know how useful my VM is going to be at measuring that small and brief of a voltage, but we'll see what happens.
One other thing - What are the odds of the trigger problem being in the magneto rather than the coil itself? I've tapped it with a small screw and felt no pull from it at all..