Monza Jr 160 wiring questions

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CincyMoto
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Joined: Tue Sep 19, 2017 2:36 am

Monza Jr 160 wiring questions

Postby CincyMoto » Mon Mar 30, 2020 12:50 am

Hello all,
My first post here.
I have a 1965 Monda Junior 160 that a local guy wired up for me. He assured me he knew the bike well and had restored one recently. I eventually learned he did not know this bike very well. I question if he can read much at all really. Many wires disconnected and others not matching up to the stock wiring diagram. Long story short. He wired it up enough to run but there are many problems. I'm looking for help on getting the wiring back to stock & proper.

Some of the things that don't work:
Low beam (High works)
Parking Light
Horn
I don't think there is a fuse anywhere in the circuits.
I don't think there is a diode anywhere in the circuits (#6 of the standard wiring diagram)

The three wires coming to the terminal block from the stator are all naked with no insulation (until it goes back a couple of inches to the main insulation) and nothing is connected to the opposite side of the terminal block. (i'd like to know how to test them to determine which are which. Temporarily I'll add electrical tape or liquid tape. Eventually I'll pull apart the stator and replace with new 3 wire harness)

I'm wondering if anyone has a stock Monza 160 and would be willing to open up their headlamp bucket and photograph the internal wiring for my reference?

Also a photo of the wiring at the terminal block would be a good reference for me to view.

I'm considering rewiring everything from the terminal block up to the headlamp bucket with new 14 gauge wires of stock color. Just need to get some reference photos to start with that correspond to the stock wiring diagram in the workshop manual.

I'll gather some photos of the current state of affairs and share them in another post.

Thank you!
- Tim
Last edited by CincyMoto on Mon Mar 30, 2020 1:53 am, edited 2 times in total.

CincyMoto
Posts: 3
Joined: Tue Sep 19, 2017 2:36 am

Re: Monza Jr 160 wiring questions

Postby CincyMoto » Mon Mar 30, 2020 1:51 am

A few photos of its current state. Ground from battery goes to rear brake switch, then back up to rear tail light along with red wire... And up to the right terminal block port. Then up to the main wiring harness by what looks like a faded orange wire?

Red positive battery lead hacked into main wiring harness with the blue splicer.
Blue wire coming out of the main wiring harness not connected to anything.
Several black wires from main harness not connected.

Headlamp bucket. Wires coming from the switch harness are coming from the right side. Wires from the main wiring harness are on the left. As you can see, its a real mess. I think he was guessing on a lot of it.
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Duccout
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Location: Essex UK

Re: Monza Jr 160 wiring questions

Postby Duccout » Mon Mar 30, 2020 7:06 am

Hi,

Yours is a story only too common. Why do some people claim that they can deliver a service, but patently cannot?

There is a company in Italy who trade on eBay who make new wiring harnesses for vintage Ducatis and even if they do not have one specifically for the Monza Jr, I suspect that another model from the same era would be the same, or easily adaptable. These harnesses are very cheap and would certainly be my first port of call (although Italy is in lock down at the moment). The other option would be to remove what is left of your harness and give it and the wiring diagram to a harness maker.

Ventodue
Posts: 952
Joined: Mon Mar 08, 2010 3:23 pm
Location: Montpellier, France

Re: Monza Jr 160 wiring questions

Postby Ventodue » Mon Mar 30, 2020 8:15 am

Yeah, that really is Amateur Hour ... :shock: :D

Not having a 160 Monza,I can't help you with your specific requests. But the good side is that there's nothing very complicated on these bikes.

Colin's suggestion of getting a new harness is worth considering. FWIW, my advice is not to get to too hung up on originality; and to make sure you use quality connectors - you can do better than using 'chocolate block' terminal connectors, for example.

Jon Pegler
Posts: 459
Joined: Sun May 16, 2010 6:19 pm

Re: Monza Jr 160 wiring questions

Postby Jon Pegler » Mon Mar 30, 2020 8:45 am

I've re-wired many Ducati singles over the years and always made up my own wiring harnesses.
The one exception was when I re-wired a 1960 Elite.
As it was cheap, I bought a new harness from Italy, thinking all would be as original, as claimed.
Many of the colours did not match the diagram and by the time I'd modified it to fit a 12 Volt alternator and regulator/rectifier unit I would have been better off making it myself.
Moral of the story, just because they say it fits your bike doesn't mean it's correct.
I will certainly not be buying another.

A 160 harness is so basic it can be made up in an hour or so, running wires point to point.

Jon

CincyMoto
Posts: 3
Joined: Tue Sep 19, 2017 2:36 am

Re: Monza Jr 160 wiring questions

Postby CincyMoto » Mon Mar 30, 2020 10:56 pm

Jon Pegler wrote:A 160 harness is so basic it can be made up in an hour or so, running wires point to point.

Jon

Yep, I'm capable. I paid him to do the job because I knew he needed the money and his price was cheap (you get what you pay for!!)
I have good connectors and crimper from http://www.vintageconnections.com/ - It seems simple enough so I don't plan to buy a pre-made one. However, I'd love to see if there are any major items missing in the headlight bucket.

Also, how to test the stator wires to determine which are which, since the color coding is gone.
And also, what about the diode? Do you have a link to one you suggest?

Thanks Jon and everyone.
Tim
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DucMonzter
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Re: Monza Jr 160 wiring questions

Postby DucMonzter » Tue Mar 31, 2020 2:39 am

Hi Tim,

I was able to locate some headlight wiring photos from my Monza Jr. - taken a few years ago. My bike is the earlier style but the wiring should be similar to yours. With the exception of a non-original light bulb in place of the parking light lens, the rest of the wiring appeared to be undisturbed when I disassembled it. Unfortunately, I couldn't find any photos of the terminal block from when things were apart - it's currently obscured by the bodywork.

On my bike, which is wired according to the original wiring scheme, the parking light, horn, and brake light circuits are powered from the battery. All other circuits are powered by the magneto when the engine is running.

'Hope this helps...
Jeff
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Ventodue
Posts: 952
Joined: Mon Mar 08, 2010 3:23 pm
Location: Montpellier, France

Re: Monza Jr 160 wiring questions

Postby Ventodue » Tue Mar 31, 2020 8:17 am

CincyMoto wrote:And also, what about the diode? Do you have a link to one you suggest?

Hi Tim

Have a look at this thread here:
viewtopic.php?t=1645

Of particular relevance is DewCatTea-Bob's (RIP) post of Jan 31 2014 from which I quote:

"" I ordered a 35A 100V and it works just perfectly, although it is a bit bigger. "

____ That's WAY-overkill, as a much smaller 4-amp/50v power-diode would be more than sufficient for the job, and could be had from any Radio Shack for under 2-bucks ! "

Ventodue
Posts: 952
Joined: Mon Mar 08, 2010 3:23 pm
Location: Montpellier, France

Re: Monza Jr 160 wiring questions

Postby Ventodue » Tue Mar 31, 2020 8:33 am

CincyMoto wrote:The three wires coming to the terminal block from the stator are all naked with no insulation (until it goes back a couple of inches to the main insulation) and nothing is connected to the opposite side of the terminal block.

This confuses me, Tim. As I understand it, your bike's original ignition system ran off an unrectified AC supply generated by an ignition coil in the stator. It won't work if this circuit is broken at the terminal block - ?

Has the bike be modified to run off a battery?

Ventodue
Posts: 952
Joined: Mon Mar 08, 2010 3:23 pm
Location: Montpellier, France

Re: Monza Jr 160 wiring questions

Postby Ventodue » Tue Mar 31, 2020 8:43 am

CincyMoto wrote: Also, how to test the stator wires to determine which are which, since the color coding is gone.

I'm finding nothing in the printed literature to indicate that the two coils in the stator are wound differently. Someone with more 'real world' knowledge may be able to say otherwise, however ..

But if it is the case, then trying to identify which is which by resistance testing won't work.

Looking at your photos, what I would do is too simply cut back the thick black outer insulation of the grouped 3 wires until you get to a point where the individual wire insulation is still intact. You're going to have to do this anyway to replace the insulation on the 3 individual wires, so there's no harm done ...


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