Bronco 125 No Spark Issues

[mtraikov]

Hey everyone! Thank you for allowing me to join this community. I have a new to me Bronco 125 that i have 3 weeks to finish up for a wedding.

I'm having issues getting spark. I reviewed the wiring and the only thing I can see possibly wrong is according to the wiring schematic there should be two wires from the hot side of the coil - one wire up to the key, and the other down into the condenser. I only have one up to the key from the hot side of the coil. I attached pictures for reference on what it looks like on my bronco right now. Does it look correct?

If i am missing that wire from the hot side of the coil down to condenser, where exaclty do i solder/splice it in ?

There are also two wiring schematics floating around, i'm not sure which is correct as both appear to be different with the wire paths?

Thank you for any help,
Mike

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[mtraikov]

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[Jordan]

Have you mixed up the HT coil terminals?
In any case, rather than connecting the condensor to the "live" coil terminal, try moving it to the coil terminal connected to the points.
Alternatively, the condensor can be connected to the points terminal post.

[mtraikov]

Have you mixed up the HT coil terminals?
In any case, rather than connecting the condensor to the "live" coil terminal, try moving it to the coil terminal connected to the points.
Alternatively, the condensor can be connected to the points terminal post.

Thanks for the info Jordan. I’m new to these older bikes. Some of the terms are still confusing to me. Where are the points located? And what does HT stand for? And where is the points terminal post?

Thank you,

Newbie

[JimF]

HT is a reference to the High Tension (high voltage) terminal of the coil: the fat wire that leads to the spark plug.

The points along with the condenser are under a metal disk on the side of the engine, but don’t mess with them yet unless you have a timing disc as the points open and close in a critical relationship with the engine’s rotation.

Generally speaking the points wire comes out from under the points cover and attaches to one of the coils two small terminals. The other small terminal of the coil needs to go the motorcycle’s electrical power: but it will likely go through the key switch allowing you to turn power on and start the bike, and to turn power off.

Most motorcycles also have a kill switch which might use a wire attached to the same coil terminal as the points wire terminal. The kill switch will short (ground) the wire to the frame when pressed which will kill the engine.

Follow the points wire up to the coil. If another wire is there follow it. I would expect it would lead you to a kill switch.

Follow the wire coming off the other side of the coil. I expect it will go to the ignition switch. If that’s the case you could disconnect the wire at the switch and connect it the positive (+) terminal of a 6-volt lantern battery. You would then connect the negative (-) terminal of the battery with a wire to the motorcycle’s metal frame. This will allow you to try and start the bike.

If it doesn’t start we can talk about pulling the spark plug out and checking for spark.

Jim

[ducwiz]

I do not own any pushrod Ducati, but was always interested in them, especially the Cucciolo. So I collected some information about these special singles.
On the web information is available, from https://groups.io/g/ducatipushrodsingles/topics and https://ducatipushrodsingles.org/. The latter keeps a lot of manuals and parts lists, for the Bronco and other models as well. The Bronco manual contains an electric scheme and the key list. This might help a lot with problem tracing.
I just signed in and realized that you have already signed up there, so you have access to all documents.

cheers Hans

[mtraikov]

HT is a reference to the High Tension (high voltage) terminal of the coil: the fat wire that leads to the spark plug.

The points along with the condenser are under a metal disk on the side of the engine, but don’t mess with them yet unless you have a timing disc as the points open and close in a critical relationship with the engine’s rotation.

Generally speaking the points wire comes out from under the points cover and attaches to one of the coils two small terminals. The other small terminal of the coil needs to go the motorcycle’s electrical power: but it will likely go through the key switch allowing you to turn power on and start the bike, and to turn power off.

Most motorcycles also have a kill switch which might use a wire attached to the same coil terminal as the points wire terminal. The kill switch will short (ground) the wire to the frame when pressed which will kill the engine.

Follow the points wire up to the coil. If another wire is there follow it. I would expect it would lead you to a kill switch.

Follow the wire coming off the other side of the coil. I expect it will go to the ignition switch. If that’s the case you could disconnect the wire at the switch and connect it the positive (+) terminal of a 6-volt lantern battery. You would then connect the negative (-) terminal of the battery with a wire to the motorcycle’s metal frame. This will allow you to try and start the bike.

If it doesn’t start we can talk about pulling the spark plug out and checking for spark.

Jim

So I have one wire from the positive side of the HT coil to the key. Then from the key it goes down to the terminal block, and continues down into the flywheel area where the condenser is located. The other small terminal of the HT coil is grounded to the frame.

I have nothing from the points to the ignition coil.

Thank you for all the explanation and info it is very helpful!

[mtraikov]

I was able to get spark, when I bypassed the key switch.

I basically took the dark green wire and extended it to the live terminal of the HT coil.

However I only got spark once and wasn’t able to recreate it. When I tried kickstarting nothing happened.

Any advice?

[JimF]

Hi Mike,

The points and the condenser are physically next to each other and electrically connected together under the points cover. The wire going to the condenser is also going to the points.

How did you assess that you had one spark and then no more?

I personally find it hard to see the spark in daylight or hear its ‘snap’ above the ambient noise when kicking the engine over.

My method is to pull the plug out of the head. With the plug wire attached to the spark plug cap, I take a roughly 24” (60 cm) wire with a Mueller clip attached at both ends, and attach one clip to the metal body of the plug and another to any engine metal that the Mueller clip’s jaws can grab.

I’ll position the plug where I can see it while standing at the kickstart lever.

Next I’ll darken the garage by closing the garage door and turning off the garage lights in daytime, or at nighttime turning off the garage lights.

When I’m standing alongside the bike grabbing the handlebars and kicking the engine over it’s easier to see the spark under the low ambient light condition.

I’m only checking with you regarding the spark situation to be sure that subsequent diagnostic advice and efforts offered by me and others are not misdirected.

You said you saw spark once and then not again, and that’s unusual.

Jim

[Jordan]

There's a wiring diagram in the operator's manual for the Bronco 125 here:

http://oldtimerworkshop.com/files/Ducati_Bronco.pdf

It shows item 10 as a container for both the points and condensor.
Both these components are earthed, and have a common wired connection, so are in parallel electrically.

This should be a good guide as to how things should be connected.
Be sure that the points/condensor wires are not grounded, by having the insulating washers and bush in the correct order at the fixing screw, which I earlier described as a post (not really the best term, sorry).

Good luck, and if it works mention us to the bride & groom.