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Author Topic: 68 Ducati 250 SSS minus an S  (Read 4563 times)

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68 Ducati 250 SSS minus an S
« Reply #40 on: Feb 17, 2018, 12:51:07 »
Black wire Ac voltage 4.35


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« Last Edit: Feb 17, 2018, 12:52:45 by Texasstar »
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68 Ducati 250 SSS minus an S
« Reply #41 on: Feb 17, 2018, 12:53:25 »
Green wire Ac voltage 8.67


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And though she be but little, she is fierce - WS
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Third Times a Charm cb175
http://www.dotheton.com/forum/index.php?topic=66169.0

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Honda Cb200 Lucky!
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Re: 68 Ducati 250 SSS minus an S
« Reply #42 on: Feb 17, 2018, 12:55:29 »
To me that looks like a typical replacement for the original wires that were likely trashed years ago. I doubt it had anything to do with trying to match colors, that's just what was available in that type of wire.

I don't know what a derivation terminal block is, but that's not a diode it's a fuse.
Thank you the derivation terminal was listed on the wiring diagram. Now I know what an Italian fuse looks like!


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It's an optimization exercise and not a maximization trip.-Teazer


And though she be but little, she is fierce - WS
http://zoomwithzeke.com/
Third Times a Charm cb175
http://www.dotheton.com/forum/index.php?topic=66169.0

Honda Cb175 Victoria!

www.dotheton.com/forum/index.php?topic=52299.0

Honda Cb200 Lucky!
http://www.dotheton.com/forum/index.php?topic=45872.0

Bultaco El Montadero 360

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Re: 68 Ducati 250 SSS minus an S
« Reply #43 on: Feb 18, 2018, 02:45:08 »
Wow DewCatTea Bobís posts on Motoscrubs are amazing! Sorry to hear about his passing but thank goodness for Forums like DTT and Motoscrubs to capture and preserve Bobís genius and legacy! 


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It's an optimization exercise and not a maximization trip.-Teazer


And though she be but little, she is fierce - WS
http://zoomwithzeke.com/
Third Times a Charm cb175
http://www.dotheton.com/forum/index.php?topic=66169.0

Honda Cb175 Victoria!

www.dotheton.com/forum/index.php?topic=52299.0

Honda Cb200 Lucky!
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Bultaco El Montadero 360

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68 Ducati 250 SSS minus an S
« Reply #44 on: Feb 18, 2018, 10:23:13 »
Stage Right enter DewCatTEA Bob as Jay Leno says, "there is always a guy who is an expert in it"

So we found a Ducati Scrambler String with a similar wiring set up as ours and both are not stock as the diagram shows above.

http://www.motoscrubs.com/forum/viewtopic.php?f=3&t=2091&p=15738&hilit=28+watt+system#p15738

So here is the background info on our bike. We know it is above engine number 92172 and were are using the correct diagram in the Ducati Workshop Book.

We know that Mick Walker's Ducati Singles Restoration does not take in account the Ducati Scramblers for the use of a Diode and said it was "only fitted to the 160 Monza Junior"

We have been very curious why Ducati chose to go to a 28 Watt system from a 40 watt system but we think we know the answer to that now. It was to balance the system so Ducati didn't need to use a Reg/rec.

So here are our findings all three wires from the case have continuity with each other.

If you ground the ohm meter to the case

White wire has 1 ohm
Green wire has .5 ohm
Black wire has .2 ohm

at idle doing the same procedure

White wire 21vac
Green wire 8 vac
Black wire 4 vac

According to DewCatTea Bob the wire with the 1 ohm should be the ignition circuit.

He also said that the Green label
Ducati coil which is an AC coil should have a resistance of 1 amp however we have two of those coils and they are both reading what they guy in the post got on his 3.8-4 ohms. Now the new 6 volt coil we started the 250 Ducati Scrambler Wide Case  Scrambler with has 1.8 ohms closer to what Bob said. Once our neighbors wake up will will fire the Duc up and test the white wire to see if it will start it without a battery.  We wired it with the white and point going to the positive on the coil and we wired the negative to ground on the frame. We know the bike runs great and starts great because we first started it on total loss the only difference is the coil need to be wired differently with the positive of the battery going to the batter and the negative going to the points and condenser. Don't ground the negative to the frame it won't start!

DewCATtea Bob is the dude. I am pretty sure he is giving Ducati rides in heaven. RIP
« Last Edit: Feb 18, 2018, 11:35:47 by Texasstar »
It's an optimization exercise and not a maximization trip.-Teazer


And though she be but little, she is fierce - WS
http://zoomwithzeke.com/
Third Times a Charm cb175
http://www.dotheton.com/forum/index.php?topic=66169.0

Honda Cb175 Victoria!

www.dotheton.com/forum/index.php?topic=52299.0

Honda Cb200 Lucky!
http://www.dotheton.com/forum/index.php?topic=45872.0

Bultaco El Montadero 360

http://www.dotheton.com/forum/index.php?topic=64349.0

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Re: 68 Ducati 250 SSS minus an S
« Reply #45 on: Feb 18, 2018, 11:39:33 »
DewCatTea bob was correct!


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It's an optimization exercise and not a maximization trip.-Teazer


And though she be but little, she is fierce - WS
http://zoomwithzeke.com/
Third Times a Charm cb175
http://www.dotheton.com/forum/index.php?topic=66169.0

Honda Cb175 Victoria!

www.dotheton.com/forum/index.php?topic=52299.0

Honda Cb200 Lucky!
http://www.dotheton.com/forum/index.php?topic=45872.0

Bultaco El Montadero 360

http://www.dotheton.com/forum/index.php?topic=64349.0

Offline farmer92

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Re: 68 Ducati 250 SSS minus an S
« Reply #46 on: Feb 18, 2018, 12:12:05 »
In regards to AC vs DC coils,
Coils are coils and they are both transformers.

A coil from a cdi ignition will be getting a substantially higher voltage from the cdi box than it would from a battery on a points system.

In order to have the same voltage at the spark plug, the inductance of the primary circuit must be different. This is achieved with either different cores, different size windings, different number of windings etc.

Long story short, running coils from a points system with a CDI might cook it, and vice versa might not spark as well.

Itís easy enough to compare if you have a known AC voltage source, you can hook it up to the primary side and see what voltage comes out the other. The ratio of resistances would also be a good indicator before hand as the relationship between resistance and the number of loops in the windings is linear (given the same gauge wire is used in both).

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Re: 68 Ducati 250 SSS minus an S
« Reply #47 on: Feb 18, 2018, 21:25:10 »
we test the other two circuits coming off the Ducati 28 watt magneto alternator.


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It's an optimization exercise and not a maximization trip.-Teazer


And though she be but little, she is fierce - WS
http://zoomwithzeke.com/
Third Times a Charm cb175
http://www.dotheton.com/forum/index.php?topic=66169.0

Honda Cb175 Victoria!

www.dotheton.com/forum/index.php?topic=52299.0

Honda Cb200 Lucky!
http://www.dotheton.com/forum/index.php?topic=45872.0

Bultaco El Montadero 360

http://www.dotheton.com/forum/index.php?topic=64349.0

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68 Ducati 250 SSS minus an S
« Reply #48 on: Feb 18, 2018, 21:27:52 »
In regards to AC vs DC coils,
Coils are coils and they are both transformers.

A coil from a cdi ignition will be getting a substantially higher voltage from the cdi box than it would from a battery on a points system.

In order to have the same voltage at the spark plug, the inductance of the primary circuit must be different. This is achieved with either different cores, different size windings, different number of windings etc.

Long story short, running coils from a points system with a CDI might cook it, and vice versa might not spark as well.

Itís easy enough to compare if you have a known AC voltage source, you can hook it up to the primary side and see what voltage comes out the other. The ratio of resistances would also be a good indicator before hand as the relationship between resistance and the number of loops in the windings is linear (given the same gauge wire is used in both).
That is good stuff! We use 5ohm coils on our Dyna S electronic ignitions on our other bikes.

Ducati used two different coils one that worked with the Ac Mag and the other with the Dc system.


You would have to reference the other link DewCatTea Bob said that the Ac coils had a lower resistance of around 1 ohm.





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« Last Edit: Feb 18, 2018, 21:33:38 by Texasstar »
It's an optimization exercise and not a maximization trip.-Teazer


And though she be but little, she is fierce - WS
http://zoomwithzeke.com/
Third Times a Charm cb175
http://www.dotheton.com/forum/index.php?topic=66169.0

Honda Cb175 Victoria!

www.dotheton.com/forum/index.php?topic=52299.0

Honda Cb200 Lucky!
http://www.dotheton.com/forum/index.php?topic=45872.0

Bultaco El Montadero 360

http://www.dotheton.com/forum/index.php?topic=64349.0

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Re: 68 Ducati 250 SSS minus an S
« Reply #49 on: Feb 19, 2018, 06:22:00 »
This is on the tinkering list.
It's an optimization exercise and not a maximization trip.-Teazer


And though she be but little, she is fierce - WS
http://zoomwithzeke.com/
Third Times a Charm cb175
http://www.dotheton.com/forum/index.php?topic=66169.0

Honda Cb175 Victoria!

www.dotheton.com/forum/index.php?topic=52299.0

Honda Cb200 Lucky!
http://www.dotheton.com/forum/index.php?topic=45872.0

Bultaco El Montadero 360

http://www.dotheton.com/forum/index.php?topic=64349.0