OX66 225 coil packs

[boscoe99]

The charge coils and the lighting coil(s) produce electricity inside them whenever magnets go wizzing by the coils. The coil wires are insulated so as to be kept apart from one another and from ground. If the insulation gets damaged by something external, or by simply physically breaking down with age, then current can flow either to ground or to other coils of wire. There is a lot of vibration on the coils due to their being mounted on the power head. With damage to the wires within the coil, heat is produced and the temperature rises until something burns. Not uncommon at all. Just comes with the territory of electrical generators and motors.

[Parker2510_OX66]

So my other post was tagged as spam because I edited it too much and is waiting approval.

After I installed the new stator pack The CDI outputs were 50-70 at crank. Below spec. Move to test Charge coil
Charge coils test out at 150VDC at crank and 223VDC idle. Above Spec. Move to test Lighting coils
Lighting coils test out between the following voltages: 3.5 - 4.5 at crank. Above spec. Replace the CDI per the manual.
At crank was with the spark plugs in the motor. Take them out and the motor spins faster giving you the potential for faulty readings.

Now, based on the shop manual test procedure and Logic, there is something in the CDI that regulates the voltage coming off the Charge coils OR There is something in the CDI that has gotten weak and is easier to charge, IE a capacitor for each of the charge coils. Hence my question above about the CDI, is there a regulator in the CDI. Likely the capacitors in the CDI, if there are, Its anyone's guess since there is ZERO schematics for the CDI on the internet. So I am left with buying a CDI to determine the cause of my issue instead of being able to review the schematics of the CDI to determine the fault and confirm it.


I have learned quite a bit about this motor just by reading posts on this forum. A lot of smart guys on here. Shop manual and test harnesses are a definite plus for trouble shooting.

[boscoe99]

With a new stator installed how is the motor running? Or have you replaced the stator yet?

AC voltage to the charge coil is unregulated. The AC voltage is what ever it happens to be. The AC voltage will change as a function of the speed of the magnets passing by the charge coil(s). AC voltage is converted to DC voltage and stored in a capacitor. When a pulser coil tells the capacitor to discharge its DC voltage to an ignition coil the voltage in the primary side of the ignition coil will induce a much higher voltage in the secondary side of the ignition coil. When the voltage rises enough a spark will jump across the electrodes of the spark plug. Thus the term capacitor discharge ignition for what is used in your model to cause the spark plug to do its magic.

The lighting coils have nothing whatsoever to do with the ignition system. They are there to create electricity to charge a battery or to light some light bulbs.

Here is a description on the OX66 charge coils.

Charge Coil
There are two charge coils located under the flywheel. They operate in tandem to supply power to the Capacitor Discharge Ignition System (CDI).
They are the only source of power for the CDI system making it a battery-less ignition system. Should either of the coils fail, the microcomputer
will default to the bypass mode and ignition timing will be fixed at 7° BTDC. The fuel system still requires a minimum of 9 volts for the engine’s
VST fuel pump to run.

[boscoe99]

Oh, the voltage specifications that Yamaha usually provides are minimums only. Higher voltage is normally not a problem. If so, then a min and a max value will be stated.

You start by checking the source of the voltage. In your case, the charge coils. If they are low (and the motor runs poorly) then it would indicate something as being amiss within the charge coil portion of the stator. In which case the stator is replaced. Now if the stator output is acceptable but the CDI output is not acceptable (CDI output is based on the stator input) then the CDI is suspected of being a problem. If the CDI output is acceptable but the ignition coil output is not acceptable then the wiring to the coil, the coil itself, of the wire from the coil to the plug is suspected of being a problem.

[99yam40]

manual should have loaded and unloaded voltage specs also.(unloaded means disconnecting from the system to see if something loading it down)
also should have with minumum RPM spec while cranking
so do not see how it would give bad info when spinning faster

I would think 3.5 - 4.5 for lighting coil voltage would be way low, but maybe I am wrong

[Parker2510_OX66]

This line is incorrect:

Lighting coils test out between the following voltages: 3.5 - 4.5 at crank. Above spec. Replace the CDI per the manual. Lighting coils should be 14v per my yammy manual, but have nothing to do with my issue. Type-O on my part by stating lighting coils.

And should be:

Pulsar coils test out between the following voltages: 3.5 - 4.5 at crank. Above spec. Replace the CDI per the manual.


Thanks for the resistance values for the charge coils. I could not find those in my shop manual. I will try to check the resistance of the Charge coils tomorrow at some time. If AC voltage is coming off the charge coils then there will be a rectifier within the CDI to change it to DC voltage. Behind the rectifier would potentially be a regulator and a capacitor. Again, unless someone has a schematic of my CDI, there is no way to effectively troubleshoot the CDI. at this point, It is a replacement part to verify that it is what caused the charge coils to fry. I really don't want to buy another part that "rarely" goes bad so I need to completely understand what caused the charge coils to fry. If things are still out of spec, its likely the incident can happen again.

[99yam40]

Thanks for letting us know of the mistake.
as Boscoe has said specs are minimum so over should be no problem, just need to know some things

what service manual do you have ?
I am guessing an aftermarket.
and what test equipment are you using?
what setting are you putting the meter on?
please answer them so we are all on the same level

[Parker2510_OX66]

what service manual do you have ? Yamaha service manual. Part number LIT186160202. Covers the SX, VX, and LX 225 and 250's

what test equipment are you using? Klein Multimeter and a DVA peak adapter. I also have several Yamaha test harnesses. Paper clips and poking holes in wires is a pain in the ass.

what setting are you putting the meter on? DC voltage as the shop manual says to test the components. Been using a MM since before we had DMM's. I even have an old analog one laying around. I also double checked the meter by testing a 9v battery. Last DMM I had was no where close to correct so I use batteries to check voltage to verify the meters are working correctly.

[99yam40]

I am very suprized that your manual did not have the info Boscoe posted,
maybe you just did not find the right place to see those specs

Sounds like you have the proper test equipment.
the DVA adapter should be just a diode,resister, and capacitor to let the voltage build up to a certain point to be measured to compare to the spec in manual
test loaded and unloaded as the manual calls for, as that will let you know if something in the system while hooked up is dragging it down

[zenoahphobic]

Don't blow up another stator coil. As already pointed out the power that caused the burning in all likelihood came from upstream, the only source would have been the battery.
The only way the battery can " flow" backwards is through the rectifier . If this is the case the diode(s) is faulty. Now they can go short circuit passing power back down to the coil(s), things heat up and then maybe the diode goes open circuit.
I am just saying this because either way the rectifier needs to stay intact if damage again is to be avoided, particularly as I see that high voltages have been measured.
I don't know about the circuits of this engine, but gathering from the posts here the rectifier/regulator is within the CDI unit, so it may very well be your next purchase.
Just shedding a bit of light onto something not mentioned to date, thorough testing to determine the original fault cause, may not in the end help you.

[99yam40]

Zeno he says he is dealing with the charge coils that feed the CDI for ignition not the lighting coils that put voltage into the battery thru the RR.
and the RR is not in the CDI

[Parker2510_OX66]

I am very suprized that your manual did not have the info Boscoe posted,
maybe you just did not find the right place to see those specs

Sounds like you have the proper test equipment.
the DVA adapter should be just a diode,resister, and capacitor to let the voltage build up to a certain point to be measured to compare to the spec in manual
test loaded and unloaded as the manual calls for, as that will let you know if something in the system while hooked up is dragging it down

My guess is its someplace in the manual that I haven't looked. They aren't laid out anything like you would expect. So I am also still learning the manual.

If I am correct a load test would be underway. Not likely ill do that anytime soon since the cold weather just moved into VA. However, I do plan on checking the resistances. Did not get to it today.

[99yam40]

I have wrote it a couple of times and I would think the manual would have the info also,
loaded is with all of the electrical components hooked up sitting in the drive way if that is where you are testing.
but then you should not be running more that the 1500RPM like that.
over that you do need to have a load on the motor, like a test wheel if not moving in the boat

[zenoahphobic]

Zeno he says he is dealing with the charge coils that feed the CDI for ignition not the lighting coils that put voltage into the battery thru the RR.
and the RR is not in the CDI

Right you are. Wondering why would the RR be integrated with the CDI.
I thought I just hurt my foot when I fell into my pool fully clothed yesterday, I must have also hit my head.

[Parker2510_OX66]

I have wrote it a couple of times and I would think the manual would have the info also,
loaded is with all of the electrical components hooked up sitting in the drive way if that is where you are testing.
but then you should not be running more that the 1500RPM like that.
over that you do need to have a load on the motor, like a test wheel if not moving in the boat

that's the load test I have been running. I use a 100 gallon tub to run it in. 1500 rpm in the drive way