Author Topic: Mille non corre -- Riparato!  (Read 930 times)

Offline Testarossa

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Re: Mille non corre -- Riparato!
« Reply #30 on: June 29, 2021, 01:22:28 AM »
Quote
What I suggest is to add a dedicated relay powered directly by the battery positive via a 10 amp fuse. This separates the ignition from the rest of the electrical system, and would be easy to diagnose if the the ignition fails.

That's what I wound up doing.

But the ultimate problem may be the coils. I measured a 1.2v drop across the coils (11.4v) and the multimeter says they're 4 ohm units. Dynatek and Dave Richardson recommend 3 ohms (Richardson thinks 1 ohm better with electronic ignitions). My 850T runs the original Bosch 3.3 ohm coils and they work fine with the Dyna III. 12.4v divided by 4 ohms is 3.1 amps, which I guess isn't enough to drive the black box. Am I missing something?

The Mille uses smaller coils, 48mm diameter, behind the left sidecover. Lucas sells 48mm 12v 3.2ohm coils, about $30 each, which would fit in the existing brackets. And Dynatek's 3 ohm coils are $150 or more per set and would require building a new bracket. Simplest and cheapest thing to do is put the points back, but installing the Lucas coils means I wouldn't have to spend an hour with the timing lights. Assuming they work.

« Last Edit: June 29, 2021, 01:23:27 AM by Testarossa »
70 Triumph TR6R, 74 850T, 74 Yamaha TA125, 89 Mille GT, 99 F650, 2013 Yamaha XT250
Gone: 59 Piper Comanche 250, 69 Harley/Aermacchi 350SS, 71 Honda CB500/4, 74 Laverda 750 SF2, 91 Suzuki VX800, 50cc two-stroke scoot, 83 XR350R

Online centauro

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Re: Mille non corre -- Riparato!
« Reply #31 on: June 29, 2021, 06:40:33 AM »
That's what I wound up doing.

But the ultimate problem may be the coils. I measured a 1.2v drop across the coils (11.4v) and the multimeter says they're 4 ohm units. Dynatek and Dave Richardson recommend 3 ohms (Richardson thinks 1 ohm better with electronic ignitions). My 850T runs the original Bosch 3.3 ohm coils and they work fine with the Dyna III. 12.4v divided by 4 ohms is 3.1 amps, which I guess isn't enough to drive the black box. Am I missing something?

The Mille uses smaller coils, 48mm diameter, behind the left sidecover. Lucas sells 48mm 12v 3.2ohm coils, about $30 each, which would fit in the existing brackets. And Dynatek's 3 ohm coils are $150 or more per set and would require building a new bracket. Simplest and cheapest thing to do is put the points back, but installing the Lucas coils means I wouldn't have to spend an hour with the timing lights. Assuming they work.

If I still had the SP today, I would certainly no longer buy Dyna coils anymore, especially at that price. The can-style Guzzi coils very rarely fail, and I would suspect the Lucas ones wouldn't either, mostly because they are oil cooled.
But you are correct about 3.1 Amps would be insufficient to operate the Dyna; the 3.1A is for each coil, which makes around 6A total; the Dyna box/pick-up plate themselves probably do not need that many amps. Larry from Dynatek told me that a 10 A fuse would handle the current requirements of the entire Dyna system, and that is why a 6-8 Amps, as a minimum, should be  expected for the whole system to work correctly.

My SP came with the Dyna and coils; I stuck with it for 20 years, but, in retrospective, if I have had a points plate, I would have reverted to that original option. BTW, I am a member of the Honda SOHC forum also, and Dyna makes a system for those bikes, as well. There is a litany of complaints on that forum about the original electrical system on those bikes to be woefully inadequate to handle the Dyna, as well. With multiple cylinders, and even with the wasted spark design, poor running from weak spark provided by the Dyna is very common. I am sticking with points and condensers, thank you very much.
Val Barone
1984 1000 SP/NT (sold)
1973 Benelli 650S Tornado (sold)
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Learn from other's mistakes ; you won't live long enough to make them all yourself.  Eleanor Roosevelt

Offline John A

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Re: Mille non corre -- Riparato!
« Reply #32 on: June 29, 2021, 11:03:59 AM »
You can get points to work out on the road. Not so much with a sealed control box. I use a relay to power coils, a relay on brake lights, headlights and so on and that has worked well for me.
John
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It is easier to fool people than it is to convince them that they have been fooled-Mark Twain

Offline Testarossa

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Re: Mille non corre -- Riparato!
« Reply #33 on: July 04, 2021, 01:13:30 PM »
Back on the road with points reinstalled, and I've learned a lot about Dyna III. Will not work with coils more than about 3 ohms. With points only, this ignition system (4-ohm coils) yields a voltage drop of less that half a volt, compared with 1.2v drop with the Dyna III box in the circuit. That box draws a lot of power.
70 Triumph TR6R, 74 850T, 74 Yamaha TA125, 89 Mille GT, 99 F650, 2013 Yamaha XT250
Gone: 59 Piper Comanche 250, 69 Harley/Aermacchi 350SS, 71 Honda CB500/4, 74 Laverda 750 SF2, 91 Suzuki VX800, 50cc two-stroke scoot, 83 XR350R

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Re: Mille non corre -- Riparato!
« Reply #33 on: July 04, 2021, 01:13:30 PM »

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