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Single-Fire or Dual-Fire ignition?

23K views 19 replies 15 participants last post by  Harryc 
#1 ·
2011 Honda Shadow Aero VT750C

Can someone please tell me if my bike has a Single-Fire or Dual-Fire ignition?


Thanks
 
#3 · (Edited)
You have two plugs per cylinder, and they both fire at the same time. That's because both plugs (for the same cylinder) fire from a single coil. That's how it shows in the wiring diagram in a 2005 shop manual. So, you got 2 coils, 1 for each cylinder.

Two plugs make a faster burn requiring less spark advance.

That's how I learned it.

Laters, C.W.
 
#9 ·
If i'm not mistaken the Shadow fires on both compression and exhaust strokes. Some call it a wasted spark system.[/QUOTE
That is correct about dual fire.
Regarding to reading of half from the real rpms your bike is single fir.
The gauge reading the sparks.So if you have a gauge for dual fire,youre bike single fire the reading are half from the real rpms.
Just my tought.
 
#5 · (Edited)
So is that Dual or single?

so far it's Dual-fire:4 Single-Fire:2

My Honda Dealer Service guy told me Dual-fire and Honda America said he "thinks" it's Single-Fire.

All I know is I bought a Tachometer, installed it and it reads 1/2 the RPM's
i.e. idling at 500 and so on. to me that says single-fire.

I can't find anyone who knows "For sure" yet.

I am trying my hardest to not use an adaptor and have to rewire it again I already have the front coil Neg going into the headlight with a lead and have already tapped into the power and lights.

Bikers Choice only sells dual-fire Tachs according to their Tech support (or Tach support lol).

I ain't buying nothin' until I know for absolute God's honest sure if the 2011 Honda Shadow Aero VT750C (Fuel injected) is single-fire or dual-fire ignition.

Remember, I got a 1/2 reading using a Dual-Fire Tach.

Thinking of just hiring a Midget to sit on my carrier rack and count the tire
revolutions and calculate the RPM's for me.;)
 
#7 ·
If I'm not mistaken, by single fire you mean one spark (both plugs at same time) for every 4 stroke cycle, then yes, it's single fire. I don't see how it can be any other way after looking at the wiring diagram. Both plugs are wired to one coil, so if it is dual spark, then it has to be with both plugs firing both times in the 4 stroke process.

Laters, C.W.
 
#8 · (Edited)
When the Person at Honda America told me he thought it was a Single-Fire ignition he said because on page 1-5 of the service manual (2011-2012) it says "Firing order Font - 308 degrees Rear 412 degrees"

Which to him meant the Coils fire each cylinder once per cycle so therefore
its a single-fire ignition. (I corrected this quote line)

Then there is the post just above yours (nraLuke) where he installed a Bikers Choice
Tach for a Dual-fire on a 2008 Honda Shadow Aero VT750 and it worked fine without having to use an adapter. But he wired his differently than I did. He went to the rear coil, I went to the front coil. He tapped into the ignition Wire, I tapped into the headlight fog light option wires for both the power and the Ignition On. I combined the ignition lead and power lead on the Tach and connected it to the Fog light option power (+) wire which is "Switched" as well and the ground to the foglight option ground wire. Is the 2008 Dual and the 2011 Single???

I got this wiring from how Cobra wires their Tachs.

I doubt it makes any difference if you wire to the Front or Rear Coil.

But on the Dual-fire ignition sytle Tach I was getting a 1/2 RPM reading,
exactly 1/2 of what it should be, no fluctuation, lights worked fine, just 1/2 of actual RPM's. This is a symptom of a Dual-fire ignition Tach being used on a single-fire ingniton System I have read in a couple places.

Again, I want to make Darn sure what I have before I do anything else at this point. Trying to avoid using the Tach Adapter for 2 reasons. 1. already have everything wired so I can get at it from the headlight area
without taking off the gas tank again. 2. I read that you get some fluctuation in the needle using the adapter.

Hiring that Midget is sounding pretty good to me now ... lol
 
#10 · (Edited)
Here's the tally so far; Dual-Fire: 5 Single-Fire: 4

:-o

I found this when I googled it today:




"People get this mixed up all the time. The number of spark plugs or ignition coils used has nothing to do with single fire or dual fire. Our bikes use two spark plugs powered by a single ignition coil, per cylinder. But this does not indicate if it's single or dual fire.
  • Single fire means the spark plugs ignite only once, which happens roughly during the beginning of the combustion stroke. (Once per every 4 strokes)
  • Dual fire means the spark plugs ignite once during the combustion stroke and once during the exhaust stroke. (Twice per every 4 strokes)
Dual fire systems don't provide any more power so there is no advantage, it was just the most simple way to run the mechanical ignition system used on older engines like early Harleys before electronic ignition control was being used. If your bike is using an electronic ignition control system, as all modern bikes seem to, then it's safe to say it's a single fire system. Some electronically controlled systems in automobiles fire during the exhaust stroke to help burn up any remaining unused fuel but this is merely for pollution control purposes. Since motorcycles don't even have catalytic converters I don't see why they would bother using dual fire for this purpose.


I know for a fact that all Shadow Spirit/ACE 750 models from 2001 to 2007 (non-shaft) are dual spark plug, single fire systems. I don't see why the C2 model would be any different."

that came from here: http://www.shadowriders.net/forums/showthread.php?t=18868


but then there is still NRALuke above with the 2008 Honda Shadow Aero VT750 haunting me with the BC Dual-Fire Tach that worked without an adapter.

Does anyone know a reliable Midget with great eyesight???
 
#15 ·
"People get this mixed up all the time. The number of spark plugs or ignition coils used has nothing to do with single fire or dual fire. Our bikes use two spark plugs powered by a single ignition coil, per cylinder. But this does not indicate if it's single or dual fire.
  • Single fire means the spark plugs ignite only once, which happens roughly during the beginning of the combustion stroke. (Once per every 4 strokes)
  • Dual fire means the spark plugs ignite once during the combustion stroke and once during the exhaust stroke. (Twice per every 4 strokes)

    I know for a fact that all Shadow Spirit/ACE 750 models from 2001 to 2007 (non-shaft) are dual spark plug, single fire systems. I don't see why the C2 model would be any different."


  • I agree with the definition of single fire and dual fire.
    I don't agree that the Spirit is a single fire system.
    The ignition pickup is off the crankshaft so the ignition module only knows when the piston is at the top of it's stroke, not whether it's at compression or exhaust.
    The single fire system needs a cam shaft sensor which according to the VT750DC manual the Spirit does not have.
    The cam shaft sensor is used to determine whether it's compression or exhaust stroke.
    That said, the 2012 model might be single fire since it's fuel injection.
    From what I understand fuel injection systems have cam shaft sensors.
 
#11 ·
Greg, All i can state is that in the add where i bought the tach it stated it was for Honda shadow aero 750 2 cyl 4 stroke 1000rpm=16.6HZ and stated in add it was a dual fire although thinking about it, logic tells me that a dual fire tach would read 1/2 RPM on a single fire system. Like i told you in Pmail, my hookup instructions are the same as the one you bought on ebay but the tach you bought states for Harley, don't know if there is a difference there or not.
 
#12 · (Edited)
I hear you Luke and thanks.

Not sure what I am going to do now but I might consider tracking down
and bikers choice tach that fit your exact description (since you don't have a record of the part number) and just pretend I am you when I install it.

But for now I am going to try and get my life OFF being totally centered
around installing a Tachometer on my Brand new Bike and try enjoying it as it is and just being totally jealous that nraLuke has a Tach and I DON"T!

LOL
 
#14 · (Edited)
Well I wish I could tell you 100% for sure as I know that is what you want to know.

Here is my take on it.

The 750 Aero I have has only 1 pickup sensor that is operated off the crank shaft, thus it is going to send one signal for every revolution of the crank shaft.

Unless the electronic control module takes that signal and knows to fire only the front cylinder on one revolution and the rear cylinder on the next then it is firing both cylinders , one will be on the compression stroke the other cylinder will be on the exhaust stroke.

That is how I think it works in these bikes but I do wish I could tell you for sure.

I might be wrong. They only have one pickup sensor however so I'm thinking dual spark.

I posted a question on the Aero 750 forum on this subject. I'll get a good answer in short order for ya.

Here is a thread from this forum that at the end says they are dual spark.
http://www.hondashadow.net/forum/72...1252-do-i-have-dual-fire-ignition-system.html
 
#16 ·
I think that the only Shadows that are really single fire would be the '85-'86 VT1100s which have two crank pulse generators PLUS a camshaft pulse gen which is used to tell compression stroke from exhaust stroke - the manual even states the cam pulser is to kill the spark on exhaust stroke. All of the other models until they switched to digital ignition are most likely "dual-fire" = spark plugs fire on every "up-stroke" whether compression or exhaust.
BTW, a wiring diagram will not show the difference...
I could be wrong since I have not read the manuals for all model years ;)
 
#18 ·
It is dual fire as it fires on compression and exhaust stroke so it halves your rpm. It is getting the signal twice in one revolution.
 
#19 ·
My two pennies,,,There is no advantage to power or anything that has to do with performance on a dual fire system, meaning the spark fires at the end of the COMPRESSION from about 12 Degree's BTDC at idle to I believe 32 degree's max advance BTDC at high rpm varies somewhat model to model. THEN IT FIRES AGAIN on the exhaust stroke. That is only an attempt to burn unused fuel for cleaner EPA reasons.

If your tach you bought was for a "dual" fire ignition, fires on compression and exhaust, and it is reading half the rpms it should then you have a single fire ignition.
 
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