Might be the terminology is a bit confusing also, could be the meaning of double VS single under one situation is different from another..The term comes from the old HD days, and may not even be relevant to the newer bikes..

Thank you Curt.

As far as why Yamaha said get a tach for a single-fire. I answered that somewhere in my previous posts. It's because we have a coil per cylinder. But our system is Dual-Fire. Thank you Scott B. for helping in this discussion.

Pfluegerak wrote:
Thank you Curt.

As far as why Yamaha said get a tach for a single-fire. I answered that somewhere in my previous posts. It's because we have a coil per cylinder. But our system is Dual-Fire. Thank you Scott B. for helping in this discussion.

Its your call, but if it were me I would wait until someone confirmed that in the manner Curt plans to. I still haven't seen any authority cited. I'm still betting on single fire. Otherwise why have two coils?

Gram

Gram wrote:
Pfluegerak wrote:
Thank you Curt.

As far as why Yamaha said get a tach for a single-fire. I answered that somewhere in my previous posts. It's because we have a coil per cylinder. But our system is Dual-Fire. Thank you Scott B. for helping in this discussion.

Its your call, but if it were me I would wait until someone confirmed that in the manner Curt plans to. I still haven't seen any authority cited. I'm still betting on single fire. Otherwise why have two coils?

Gram
I believe that if it was a dual fire the coil would be similar to this
http://www.bosch-motorsport.de/pdf/components/ignition_coils/2x2.pdf

I posted a website's description between the two a few posts up. The later bikes, including ours, are single-fire.

Here's one authority that should help clear things up. This company manufactures engine controls.

http://www.gill.co.uk/products/digital_ignition/Introduction/8_wast_spark.asp

Scott B.

Gram wrote:
Pfluegerak wrote:
Thank you Curt.

As far as why Yamaha said get a tach for a single-fire. I answered that somewhere in my previous posts. It's because we have a coil per cylinder. But our system is Dual-Fire. Thank you Scott B. for helping in this discussion.

Its your call, but if it were me I would wait until someone confirmed that in the manner Curt plans to. I still haven't seen any authority cited. I'm still betting on single fire. Otherwise why have two coils?

Gram
Gram,

What needs to proven is does a cylinder's spark plug fire once per crank revolution. That would determine the R*s ignition system type.(Dual-Fire) Which would mean the only ignition triggering device is at the end of the crankshaft. Every revolution of crank, a cylinders plug will fire. And that there are no other sensors that determine in which phase the piston is in (compression BTDC or exhaust BTDC).

Now as far as Tachs are considered, as you know, tachs just count pulses and from that, the factory has predetermined whether (1) one pulse or (2) pulses is a revolution of the crank shaft. They loosly label them as for Dual or Single fire.
And what is meant by that is, if the coil you plan to hook it up to fires once per revolution (theorizing the R* does), doing duty for 1 cyclinder only ,then order a tach for single fire. If the coil does double duty, meaning working for both cylinders, then get a dual-fire, because the number of pulses per revolution is twice that of a coil only working on 1 cylinder.

Edited/Correction
ebay tach

Purchased this item, Spec: 16.6 Hz = 1,000 rpm
16.6 Hz = 16.6 pulses per second, 16.6 x 60 sec/min = 996 pulses per minute
basically 1,000 coil pulses per 1,000 rev crank revolutions
Thus cylinder 1 firing on every revolution, BTDC compression & BDTC exhaust
reports of this tach working without single fire adapter.

What the tach manufacturer is looking for is whether or not there are 2 coil signals in 720 degrees. On the Harley there is because the trigger is driven at cam speed and the one coil is supplying 2 cylinders. On the Road Star there is to the coil the tach is hooked to because the trigger is being driven at crankshaft speed.

In the strictest sense of the word, technically the Harley is a single fire in disguise because any given cylinder only receives a properly timed spark on the compression stroke. The Road Star however receives a properly timed spark on both the compression stroke and the exhaust stroke of a given cylinder.

I'll bow out of this now since I'm the one that probably started it all and unless someone has a question for me I'll keep my own counsel. It has, at least for me, been interesting though.

Ride safe.

Scott B.

Until see Curt's hair stand on end when he gets shocked by his experiment I stand by the previous posts ... the R* is single fire and only fires on the compression stroke.

With the advent of computerized ignitions systems, in our case the ICU, things are not as obvious as they seem. The ICU controls a lot of functions that in previous mechinized engines was controlled by gears, levers and such ... magic.

If you examine the pickup rotor you'll see lobes on it, some with marks. Clockwise, the first mark is on the 4th lobe and is the advance at 10 degrees BTDC of piston #1, the next mark is TDC of piston #1 (let's call this 0 degrees) and the last is TDC of piston #2 (rotationally 402 degrees after #1). The additional lobes prior to the 10 degree advance lobe are to signal the 40 degree advance at 4000 rpm. Only three areas on the lobe are marked because those are the only ones a tech would need when working on the engine.

The lobes trigger the pickup coil on/off sending pulses to the ICU, which then sends a signal to the coil appropriate coil so fire one cylinder. How does the pickup coil know which cylinder is at TDC? ... it doesn't, the ICU counts the pulses. The first rotation of the engine fires #1; the second rotation fires #2.
That's the reason the timing on the R* is not adjustable because if it was, it would screw up the messages received by the ICU.

That's my take ...

Doc

I emailed NoPork.com about this, and got this reply:

Fw: Tach for '07 Roadstar
From: "Brian Erman" <brianerman@sbcglobal.net>


From: jimtec@aol.com
Sent: Tuesday, September 14, 2010 10:05 AM
To: brianerman@sbcglobal.net
Subject: Re: Tach for '07 Roadstar


That is correct, a Roadstar requires a single fire type tach.