Yeah, you're right. Don't know what that'd do, other than freak the dwell from the module. The Ultima kits all come with a jumper in the coil packaging to go across the trigger primary posts to use with a stock module, I assume. I always threw them in the electrical junk box...

I don't do "high performance" razors edge of max h/p work. And I'm too lazy to get degree wheels, pointers and do all that to figure it out. I know they don't fire 360 or 720 degrees apart, that won't work.

But I've always wondered about the timing of the wasted spark for each cylinder. Factory setup wouldn't be too hard to figure out but these nose cone ignition modules have 2 pickups working and computing from 2 trigger windows on the rotor. I don't know if one pickup reads a particular cylinder or one reads rpms and the other reads degrees.

Dyna tech support is excellent, but they don't have time to explain it over the phone or email, I suppose. They usually just take you where logic and the instruction sheet will lead you anyway.

 

If you look at the bottom 2 wiring diagrams in the instructions, on 1 daisy chains the primary (coils in series) and the other uses the wire to power 2 separate coils. It's interesting that the 644 runs curves that are retarded from the original Dynatec 2Ki. I would guess it was because the ultima motors are a little higher performance. I run a 2Ki in my 113 SnS at 10.8 to 1 but run curve 4 and the curve is retarded 3 degrees. My guess is that the 642 runs the 2KI

 

I understand about series/parallel resistance. This old 642 runs the same "part" curves as the D2ki. Static timed and checked with light, 1 is 35, 2/35, 3/32. 4/30. I never tried to verify the WOT (no voes signal) curves.

Spark knock under high load or acceleration (with or without voes signal) has never been an issue with my stock compression unless it was a really hot day on regular fuel and then, only on a hard clutch-out at takeoff. Most always run premium and part of the reason I put it in years ago, was so I could drop a switch/timing if I got out in the country and could only get regular.

I may never know for sure but can't help thinking that somehow, running it switched to dual fire while wired to a single fire coil may be queering the module brain and putting spark somewhere at the wrong place and/or time. Even if it only does it intermittently, that would eventually cause a problem. Been carrying a brand new spare D2ki in the saddlebags for several years. Especially if I don't find something suspect (sharp edge) with the cylinder, probably install the new one when I go back together for piece of mind.

Anyone who wrenches much will, at some point, run into a failure that defies all logic or explanation. I don't want this to be one of those, even if it turns out to be my boo-boo...

 

I don't quite understand what your saying here.. the module is doing nothing but providing a ground to trigger the primary side of the coil.. The daisy chain you mention (jumper) is only the normal power supply to individual coils.. The triggers are still separate.. and the primary side of the coils are in parallel not series..

 

It was in reference to this statement.

Dual fire uses only one primary wire.

 

I was assuming you know the difference between the series and parallel. Just pointing out the difference.

As far as how the switch could confuse the module based on how it was wired, I doubt that the module gets screwed up at all. I would bet all it does is use the switch position to figure out whether the module puts out 2 pulses on the pink for both cylinders than just 1. The blue wire looks to put only the front cylinder pulse no mater the switch position. It might put out the rear in dual fire mode but really don't know.

Now running dual fire the rear cylinder will see a spark that is 45 degrees ATDC - timing advance so worse case it might be say 40 degrees (45-5) into the intake stroke. Could that cause the fuel to start burning in the intake stroke with funky gas? If so, it could cause an issue but I'd expect you'd be getting flames out the intake..

So far all failure I've have have been explained, some took a while to figure out tho. Some took years. ;D

 

The wasted spark thing is probably a stretch, but on the other hand I seem to recall these systems were marketed as 'reducing vibration' back in the day. The theory was that the wasted sparks were lighting a small and unwanted flame. That would be far more likely to be the rear cylinder than the front. Some guys were saying they could feel the difference when they switched to single fire, others were calling bullshit so who knows? Some bikes slipping a bit more mixture than others? Or was the vibration being measured 'at the brochure'?

 

AH - HA! The blue wire definitely sends a signal regardless of switch position. Otherwise, the front would not fire if wired to s/f coil and switch set to dual. That's the deal - switch changes pink wire from 2 pulses to one. Awesome! You should get a job at Dynatek support, Max.

I've run it both ways. It never seemed to make any difference whatsoever in the running on mine. Some have claimed theirs run or starts better, probably a mental thing and never heard a fuel mileage claim.

But I have noticed lately, the exhaust tone seems different d/f vs s/f on this one at certain lower speeds. This may be a mental thing as well

 

Yeah it is.. It's only the rear cylinder that is going to see the issue. Front wasted spark on the rear cylinder is on the exhaust stroke. The early bikes (Honda 4s for example) that had 360 cranks pretty much always had wasted spark without issue.

One thing to note is that with bad gas the rear cylinder is the weakest link since it typically runs hotter.

 

We'll have to agree to disagree about that, in a way. I've used an infrared thermometer a good bit. (for cooking mostly). On mine with fairing, lowers and low slung tank, normal easy riding at about 80 degrees and stop. Cylinders frt/rr - 175/275. Heads about 210/225 Let it sit 3 minutes with no breeze and it'll read 225/245 and within 10 degrees on the heads. I've done that check many times.

Chasing an elusive intake leak 2 years ago, I carried a digital thermocouple for several rides. Same conditions as above but pulled the plugs immediately on a stop and put the probe directly on the top of the piston. The front piston would consistently be 80 degrees hotter than the rear. I'm assuming that's because the rear gets so much more oil off the flywheel. As with the cylinders/heads, after 3 minutes the piston temps are near equal.

Obviously the front cylinder/head will be cooler while riding from the air flow, but the actual piston temp is generally higher on the front... from my experiments anyway.

I'm just tickled pink we figured exactly what the #6 switch does