Drifters Single fire or Dual fire ignitions.

[mittico68]

Have you installed a tachometer on your bike?

Nope. I prefer to use my ears...
BTW, regarding what Bucko was guessing about the 800: I can confirm that she's got just one spark per cylinder.
Just my 2 cents...

[chief]

Chief, I've got an 800 but I have no skills for the question you're asking.
Anyway, if you should ever come to Italy, I'll be glad to let you check ma-deuce! 

I'll keep that in mind!  Have you installed a tachometer on your bike?

[mittico68]

Chief, I've got an 800 but I have no skills for the question you're asking.
Anyway, if you should ever come to Italy, I'll be glad to let you check ma-deuce! 

[chief]

Someone can correct me if I'm wrong but I believe the 800's have only one spark per cylinder and presumably one coil per cylinder (otherwise the ignition timing is going to be goofy for one cylinder - which I think maybe is the way that Harley did/does it ) which would make them 'single fire'.

Yeah, the differences between the 800 and the 1500 always surprises me. I really should find an 800, just to learn more about it!

[Bucko]

Someone can correct me if I'm wrong but I believe the 800's have only one spark per cylinder and presumably one coil per cylinder (otherwise the ignition timing is going to be goofy for one cylinder - which I think maybe is the way that Harley did/does it ) which would make them 'single fire'.

Edit: Single fire but they probably still fire on every stroke, including the exhaust stroke so there's still a wasted spark (depending on what the ECU is doing - if there is one on an 800?).

[chief]

So, is it your opinion 800 and 1500 Drifters are single fire or dual fire?

I believe both the 1500 and 800 Drifters are functionally dual fire. (800 is a complete guess.)

Maybe an 800 rider can educate me.

[Troll]

I just looked at the wiring diagram, you are right about the coils firing which cylinders. That being the case, it's EXACTLY like the system I installed on my SuperGlide, with one coil serving each cylinder. Never really looked at the coil setup since I haven't had the tank off in a decade.

[Bucko]

I posted this a while ago, when the topic first came up, but it disappeared. 1500s have 2 dual coils, one for each plug on each cylinder. They are waste spark. The bulk of the spark energy goes to the cylinder with fuel in it. The fuel near the electrodes of the plug ionizes and provides a path to ground for the electric charge from the coil. The other cylinder has exhaust gases in it, and they don't provide much of a path, so the spark is quite weak (waste spark) Since there are 2 plugs per cylinder, the same setup is used in tandem. 800s have one coil per cylinder, and they are single tower. They are "single fire".

Not sure your description is accurate or perhaps I'm misunderstanding it.  On these bikes, one coil feeds a pair of plugs on one cylinder, the other coil feeds a pair of plugs on the other cylinder.  The coils are triggered by timed (i.e. offset) pick-ups from the crank via the ECU.  Not sure if they fire every revolution or not (the ECU may prevent this - but I doubt it), but if they do, then both coils fire on both the compression stroke and the exhaust stroke (hence the 'wasted' spark).  The energy from both the compression spark and the wasted exhaust spark is the same - it doesn't matter which stroke it's on

The motorcycle 'Ground' is not used for firing the plugs in the same way as a single fire coil which fires from coil to ground.  On a dual fire system the motor is just part of high voltage conduction path - it's not a 'ground' relative to the coil output.  On dual output coils, the energy travels from the (+) side of the coil output down the high voltage lead, through one plug (anode to cathode), through the motor, through the other plug (cathode to anode) and back up the second plug high voltage lead to the (-) side of the coil output.  I may have 'anode' and 'cathode' direction swapped - the point is: energy flows one way in one plug and the opposite way in the second plug to complete the high voltage circuit.

[Troll]

I posted this a while ago, when the topic first came up, but it disappeared. 1500s have 2 dual coils, one for each plug on each cylinder. They are waste spark. The bulk of the spark energy goes to the cylinder with fuel in it. The fuel near the electrodes of the plug ionizes and provides a path to ground for the electric charge from the coil. The other cylinder has exhaust gases in it, and they don't provide much of a path, so the spark is quite weak (waste spark) Since there are 2 plugs per cylinder, the same setup is used in tandem. 800s have one coil per cylinder, and they are single tower. They are "single fire". I installed a true single fire system on my hotrod SuperGlide decades ago. Required 2 pick up coils and two dual tower coils. I was running two plugs per cylinder, and each coil serviced one cylinder. Here's what that looked like:

[tj]

So, in the case of a twin-plug V-twin, both plugs in the same cylinder (on the same coil output) fire at the same time.  Since the two plugs from one coil complete the high voltage circuit - they both fire with equal 'energy'.

I'm pretty sure both plugs (in a cylinder) fire for both the compression stroke and the exhaust stoke (i.e. both plugs fire a 'wasted' spark).

This is exactly the way I understand it.

[Bucko]

Dual fire shoots spark to both cylinders at the same time from an single coil. Most of the spark goes to the cylinder under compression while a smaller bit go to the exhaust stroke. There is some "wasted spark" as a result.

So, in the case of a twin-plug V-twin, both plugs in the same cylinder (on the same coil output) fire at the same time.  Since the two plugs from one coil complete the high voltage circuit - they both fire with equal 'energy'.

I'm pretty sure both plugs (in a cylinder) fire for both the compression stroke and the exhaust stoke (i.e. both plugs fire a 'wasted' spark).

[chief]

When you mention 'dual fire', is that the same as: 'wasted spark' (like on inline 2, 4, or 6 cylinder bikes)?  If ignition is triggered by crank position sensors, which I think they are, then it's likely a wasted spark, no?

Dual fire shoots spark to both cylinders at the same time from an single coil. Most of the spark goes to the cylinder under compression while a smaller bit go to the exhaust stroke. There is some "wasted spark" as a result.

[Bucko]

When you mention 'dual fire', is that the same as: 'wasted spark' (like on inline 2, 4, or 6 cylinder bikes)?  If ignition is triggered by crank position sensors, which I think they are, then it's likely a wasted spark, no?

[chief]

Opening up this topic for discussion.

Considering the age and differences of our Drifters (1500 and 800) - do our bikes have single or dual fire ignitions? Both the same? Different on 800 and 1500?

If you know the answer(s) post your info here, references if you have them.