Topic: No spark on 2-3. Bad Coil?

[gbal06]

I have no spark on #2 and #3.  I am assuming that it is a bad coil.  How do I test the coil with a multimeter to see if it is bad?  I am assuming that the reading should be above 3.0 to 3.5 correct.  If it is bad I do have a dynamic coil that I bought a couple of years back for another bike that I never got around to using but noticed it had some "bubbling" on the front of the coil.  it has never been used, so what could of caused it?  If I can still use it, can I run the old coil that is good with a 5.0ohm dynamic coil?  Thanks

[KennyRedman]

This will help:

[Stev-o]

I would bet your coils are not bad.

[gbal06]

This will help:

Thank you

[gbal06]

I would bet your coils are not bad.

What else would cause the #2/3 spark not to fire? Bad plugs?

[bryanj]

Points or condenser or dissconnected wire

[gbal06]

Points or condenser or dissconnected wire

How do you test them to see if they went bad?

[gbal06]

Points or condenser or dissconnected wire

How do you test them if the went bad?

[RAFster122s]

Likely grounding things in your points wiring which causes the coil to never build that potential but bleeds it constantly....

[gbal06]

Man you guys are great!!  I replaced the compositor for 2-3 and fired up right away!! As far as the gas pouring out of carb#4 I lightly sanded and polished up the brass hinge for the float and the float needle seat and presto!! No more pools of gas!  Thank you everybody for the tips/advice!

[gbal06]

Question does remain though. What could of melted the dyna coil if I bought it used and never has been used?

[Don R]

 Either chemical or temperature bubbled that coil. I would take "never used" with a grain of salt.

[TwoTired]

Question does remain though. What could of melted the dyna coil if I bought it used and never has been used?

When the points set is closed, current flows through the coil primary.  A 3 ohm coil fed 12-13 Volts will consume 4 to 4.33 Amps, or 48 to 52 watts.  Normally the points are only closed for about half the time, due to the rotating point cam, so average watts dissipated by each coil is ~24 to 26 watts each, and cooled by air the bike is driving through.  However, if the key switch is on while parked, a 3 ohm coil can heat up like a 50 watt lamp and builds heat if there is no airflow to cool it.

Cheers,

[PeWe]

That black coil is a 5 ohm coil.
I have that coil model on 2 bikes. I have not seen any damage like that.

It might be as answered, coil has been powered on for a long time when parked getting very hot.

[Deltarider]

Just applying Ohms Law to coils in process and then deducting the Watts consumed, is all too simple, I'm afraid. Statically seen, the calculation is correct, but dynamically it's not that simple. Some time ago I have connected, out of curiosity, an ammeter between the kill switch and the coils. I measured around 3A at idle and just a little over 2A, when revved. My coils are 3Ω in combination with - at the moment of the test - breakerpoints. Measured duty cycle at the time was around 53%. With my transistor ignition fitted, draw was just a little extra. It was in fact so little, that I didn't even bother to write it down. Anyone is invited fo falsify my dynamic test ofcourse. Please do; the more data, the better.

[ekpent]

That black coil is a 5 ohm coil.
I have that coil model on 2 bikes. I have not seen any damage like that.

It might be as answered, coil has been powered on for a long time when parked getting very hot.

Old Suzuki 2 stroke coils are pretty notorious for burning themselves out if the ignition is left on too long.

[bryanj]

What is a compositor? Did you mean capacitor ( spell check needs turning off on the forum!)

[gbal06]

Ya stupid spell check lol

[HondaMan]

Like TwoTired's analysis: I have burned up several Dyna coils on my electronic test bench, most of them due to a disconnected wire on my frequency generator that runs the Transistor Ignitions when I am burning them in. If the clip lead falls off the driver board I use, the generator simulates a "points closed" situation. In about 15 minutes the Dyna coils melt and ooze some sort of goo out, which then catches fire. So, yeah, my test bench has a buned tabletop!

I only test with the Dyna coils when I am in the room, now...

[Quattrocilindri]

I have no spark on #2 and #3.  I am assuming that it is a bad coil.  How do I test the coil with a multimeter to see if it is bad?  I am assuming that the reading should be above 3.0 to 3.5 correct.  If it is bad I do have a dynamic coil that I bought a couple of years back for another bike that I never got around to using but noticed it had some "bubbling" on the front of the coil.  it has never been used, so what could of caused it?  If I can still use it, can I run the old coil that is good with a 5.0ohm dynamic coil?  Thanks

That black Dyna coil in the middle picture is rated at 5 Ohm primary resistance. The bubbling you see is a sure sign of overheating, which means it is either dead now, or well on its way. I have had quite a few of those on my other bikes and 2 of them either failed me on the road or made my life miserable in troubleshooting a crappy running /poor starting bike.
You test them by setting the multimeter in the picture below in the Ohms mode, just as you see it in the picture from the other post. Take the two red and black probes and touch the 2 brass terminals, does not matter which probe goes to either terminal: your meter should show a reading close to 5- 5.75 Ohms for a good coil. If it is dead, you'll get no reading at all. Any other reading means that the coil is not a reliable unit.