1989 Kawasaki Bayou 300 Ignition Coil Killer

[bigd764]

I have a 1989 Bayou 300 and  i have to keep replacing the ignition coil on it. Does anyone know what might cause this ? It runs great for a few weeks and then it just stops firing and won't start back until the coil is replaced. I have put 3 new coils on it already.

[bigd764]

Oh, by the way, it has a new battery, spark plug, Cdi, and regulator-rectifier.

6 minutes ago, bigd764 said:

I have a 1989 Bayou 300 and  i have to keep replacing the ignition coil on it. Does anyone know what might cause this ? It runs great for a few weeks and then it just stops firing and won't start back until the coil is replaced. I have put 3 new coils on it already.

 

[Mech]

The wrong coils ? CDI systems have to have a coil made for them, not one made for the old 12 volt systems.

A bad earth or, if it has two wires, reverse connected.. 

Bad mounting, either distorting it, overheating it, or vibrating it too much.. All long shots because they are normally pretty tough.

Edited February 15 by Mech

[Gwbarm]

Aftermarket coils are cheaply made, iv had them bad right out of the box, if these are OEM coils made for the bike I would be greatly concerned

[bigd764]

First of all, thanks for the replies. The coil is an aftermarket and i know they are cheaply made. It's hard to find an OEM for this old ATV without paying a big price for it.

[bigd764]

The replacement coil was much smaller in size than the original. I had to drill holes in the mounting plate to get it to bolt up. It's mounted securely and i don't think vibration is the issue. It has two wires and i am not 100% sure they are reverse connected. I took a look at the service manual and it said the bike would run with the wires either way without changing performance. The original coil was marked with positive and negative terminals but the replacement was not.

[Gwbarm]

Just had another bad aftermarket coil out of the box, it wasn't completely bad but specs were not what they were supposed to be for my machine. 

[bigd764]

On 2/20/2023 at 10:55 AM, Gwbarm said:

Just had another bad aftermarket coil out of the box, it wasn't completely bad but specs were not what they were supposed to be for my machine. 

I tried testing the resistance on the coil. Could you tell me what the specs are supposed to be?

[Gwbarm]

Primary coil resistance .18-.28 ohms, secondary resistance 6-9 K Ohms.

[bigd764]

On 2/22/2023 at 10:29 AM, Gwbarm said:

Primary coil resistance .18-.28 ohms, secondary resistance 6-9 K Ohms.

Thanks. The primary resistance i get is .000 and the secondary is 10 K Ohms.

Edited February 23 by bigd764
I typed the wrong primary

[Gwbarm]

Your secondary resistance is good, when checking the primary make sure your meter is set on the lowest OHM setting.  The coil I was referring too bad right out of the box has a primary resistance of .1 OK and a secondary 0f 2700, quite low.

[bigd764]

The lowest setting i have on this meter is 200 which i think is not low enough.

[Mech]

If it was totally open circuit you should have got the infinity reading same as you do when the leads aren't attached to anything.

You could use a test light and a battery to test/confirm the primary.. It should have the test light burning brightly, as bright as straight across the battery.

[Mech]

As for having the coil either way around..  That's not so. The primary and the secondary windings both attach to the same internal earth. If it's connected the wrong way around the HT instead of earthing straight to that internal earth, has to go through the primary windings to get to earth..  That HT burns through the insulation on the windings.

It has to have the internal earth end of the primary windings going to earth..

Edited February 23 by Mech

[bigd764]

Thanks. I will try that tomorrow and post back with the results.

[Mech]

It can be that even though the test readings are right, if the insulation is not good enough to prevent the HT breaching it, then the coil can still not work..  Depends where the actual breach of the insulation occurs..

[bigd764]

55 minutes ago, Mech said:

As for having the coil either way around..  That's not so. The primary and the secondary windings both attach to the same internal earth. If it's connected the wrong way around the HT instead of earthing straight to that internal earth, has to go through the primary windings to get to earth..  That HT burns through the insulation on the windings.

It has to have the internal earth end of the primary windings going to earth..

Since the new coil doesn't have the + and - terminals marked,how do i determine which one is which?

[bigd764]

This is a diagram of the coil according to service manual.My original coil looks like this. My new coil isn't marked with + or - . So i hooked it up with the green/white wire directly across from the spark plug wire.

[Mech]

Yeah, that's the tricky part.. haha.  In the old 12v systems there was more resistance in the primary windings and you could tell which was which with an ohm gauge. The cdi coils have so little primary resistance in the primary that it would need a very accurate ohm gauge, or an oscilloscope..

I don't know how you are going to tell the difference, but I'll bet that's the problem..  That or a bad earth which has much the same effect on the coil..

If all three of the coils you've had have been aftermarket, perhaps it's time to invest in a genuine item.. If some of them have been genuine yamaha, then check the earths.