SERIOUS spark issues on a Peugeot 103

The bike:

1978 Peugeot 103 LVS, 2-coil magneto.

The story:

Long ago, my Peugeot ran fine. One fine day, I was taking her down a bit of a hill, when all of a sudden, I started losing power. She died and I hauled her to the side. She started back up, but if I gave it too much gas, it would die again. I was able to slowly get back up the hill. Some investigation told me nothing. Later that day, I was able to ride her back home as if nothing had ever been the problem. Attempts to start it after that point were totally fruitless. Several months later, I've examined virtually everything in detail, and have had others helping, and nothing has worked.

The symptom:

Spark only at high RPMs (serious pedaling). Anything slower, and spark disappears. No arcing across points.

What I've done:

Tried new plugs galore. I have installed a new condensor and new points from Handy Bikes. Condensor was soldered fairly carefully and should not have been destroyed in the process. I swapped out the entire stator plate and replaced it with another, which would hopefully rule out any coil issues, if there were any. Points open exactly when rotor mark hits stator mark. Wire continuity is fine for all of them, wire sheathing is not compromised. Points do not conduct when separated. One thing I have not checked as precisely as I could is whether the flywheel is seated at the exact position it should relative to the crankshaft (rotor and stator marks align slightly before TDC, but exactly how much before I can't quite measure with my current toolset)

I need help. What could potentially be the problem here? I'm completely out of ideas. I would really appreciate some suggestions from the wise ones, _especially_ if you have a lot of Peugeot knowledge.

Thanks for reading.

Re: SERIOUS spark issues on a Peugeot 103

Have you checked your tail light bulb or wires to your tail light?

Re: SERIOUS spark issues on a Peugeot 103


Wow, sounds you really hit the troubleshooting jackpot! Here's a few comments.

If there was already bad spark before you replaced the stator plate, I would put the old stator plate back on the engine - if it's not huge trouble to do so. You need to be careful about adding new variables (the new stator) to a troubleshooting situation, else you can end up 'chasing your tail' as we say.

Are you still using the same spark plug cap? I've seen plug caps cause a total loss of spark at low rpms.. but they kick in fine at higher rpms. If unsure, remove the old cap, clip 1/4" from the end of the plug wire, and install a nice new NGK resistor cap.

The metal Bosch caps are famous for this kind of behavior. I replace them on sight, unless they are clearly spanking-new.

Next, had you considered that the magneto rotor may have lost magnetism? Weak magnets will kill low-rpm spark quality. Specialist shops that service tractor or aircraft magnetos have equipment to re-energize weak magnets. See if one of them can do your rotor. It's inexpensive. Heat and vibration weaken magnets over time.

It's interesting that it failed on a downgrade. Going down a hill (if the throttle is mostly closed) can create a lot of vacuum, which in some designs can result in sucking-in a crank seal, manifold gasket, etc. But since spark is clearly an issue, we can put that notion on the back burner for now.

Best of luck with it; with all the knowledge available, I'm sure you'll get it sorted out.

Re: SERIOUS spark issues on a Peugeot 103

Engine is entirely disconnected from all wiring except ignition. Before doing that, I replaced both headlight and taillight bulbs.

Re: SERIOUS spark issues on a Peugeot 103

also if it dies for no good reason look at the plug. My Grand Prix Died today and after some investigation i found a deposit bridged plg to be the prob so after swiping an lottery ticket through it fired right up.

Re: SERIOUS spark issues on a Peugeot 103

Tried new plug cap, and cut 1/4" off the old, too. One is from 1978, the other from 2004. Tried a different rotor, magnetism is probably not the problem.

You're right that I haven't troubleshooted (shot?) it as well as I might have. I was just fed up and wanted the problem to go away and my bike to run, so I threw t'other on there.

I thought for a minute that perhaps my positioning of the flywheel on the crankshaft would be the issue, but then I thought...what does that have to do with spark itself? Nothing. The stator plate is fixed in place, the points are slightly adjustable, but they only move when the flywheel's cam hits them, which is fixed relative to the flywheel. So theoretically, I could have the flywheel mounted to the crankshaft in exactly the wrong way, and it should still be pumping out spark because the electrical components don't rely on the crankshaft for anything. True?

Re: SERIOUS spark issues on a Peugeot 103

The older 2-coil magneto peugeot engines are quite troublesome. The usual symtom is blowing condensors very often. You may want to upgrade to a later 5coil magneto or there is a fix that Myron's Mopeds in California does. Involves unwinding the coils so many turns.

Also have you thought about moving the condensor out of the magneto? I have heard that sometimes solves erratic ignition issues.

Best of luck!

I have a '78 103 too that suffers from varying ignition problems here and there.

Curious to see what the outcome is.....

Re: SERIOUS spark issues on a Peugeot 103

I agree. After delving into it, it seems as though there are many opportunities for wires to wear through their sheathing and ground out. I do have a 5-coil engine, and it's beautiful...but I'm saving that for another project. I'd really like to figure out the problem with this one, if I can.

Re: SERIOUS spark issues on a Peugeot 103

Does the flywheel position affect where the magnets are in relation to the position of the coils when the points open? You want the points to open when the coils are producing maximum energy, so that the spark plug arcs. If you look at the diagrams I sent you, the symptoms you're seeing may represent a misalignment here.

If your points are opening too far away from magnetic neutral, the energy sent to the plug will not be enough to cause it to arc. As you go up in RPM, you produce more energy through the coils per revolution, and the plug can arc.

Re: SERIOUS spark issues on a Peugeot 103

If you were just cruising along and it happened because of the hill... it sounds like a simple gas thingy to me....especially if it started back up for a few minutes... ir it was electrical wouldn't it just die? but it sounds like youre having fun rebuilding the ped so... what do I know lol... good luck!

Re: SERIOUS spark issues on a Peugeot 103

have you tried cleaning the carb??

Re: SERIOUS spark issues on a Peugeot 103

Spark, spark, spark is the issue. Spark test is what I'm using. It won't run without spark, that's for sure.

Re: SERIOUS spark issues on a Peugeot 103

The 5 coil magneto does not seem interchangeable with the 2 coil magneto. Specifically because the 5 coil magento flywheel is about a quarter inch wider than the 2 coil magneto (don't know if the two flywheels are interchangeable..wouldn't think so, as they have different magnet configs), and jams itself into the housing portion of the stator. The screw holes that mount the housing to the engine case orient it such that the ignition line rubs against the cylinder base. It just doens't seem to work.

Re: SERIOUS spark issues on a Peugeot 103

No, it does not affect the magnet position relative to the coils when the points open. The points are mounted to the stator and so are the coils. Neither move relative to each other (aside from adjusting the points)...therefore since the cam on the flywheel does not ever move relative to the magnets on the outer edge of the flywheel, position of the flywheel on the crankshaft should not matter. Points adjustment is the only thing you can alter that would change that. (Thanks for the diagrams, btw)

It's possible that despite setting my points exactly how they should be according to the manual, I need to monkey with them more. I'll do that and try some more.

Re: SERIOUS spark issues on a Peugeot 103

Changing the points setting to a variety of different positions did absolutely nothing to help the problem...exactly the same outcome at four different positions--early, on time, mid-late, late. At this point I can find nothing wrong with the magneto at all, unless:

1. My flywheel spontaneously lost magnetism, and the other has the same problem.

2. Coil(s) failed immediately, and coils on the other also happen to be bad.

3. Condensor failed, and despite my best efforts, the new one is defective/destroyed as well.

4. Old, new, and other set of used points are all defective, despite conducting fine while closed, and not conducting while open.

The only other thing I can think of is that wiring outside of the igntion (lights, horn, etc), when disconnected, affects ignition. The only way I think I can determine that is by getting some kind of wiring diagram. The wiring diagram in the owner's manual sucks. Anyone want to help me out by scanning a proper one in?

Re: SERIOUS spark issues on a Peugeot 103

Never mind, I found a manual. I'll look through in more detail.

Re: SERIOUS spark issues on a Peugeot 103

No problem with the diagrams, I've been meaning to send them to you for a while. I guess having the relative positions fixed like that is nice since the spark timing theoretically can't get out of whack, but you can't tune it either...

You could experiment with various points settings to see if that improves the spark at all. Doesn't see too likely though.

This problem is certifiably weird.

Re: SERIOUS spark issues on a Peugeot 103

I had same prob. with my 77, but it would not start and run again, that would probably be fuel.

my flywheel had slipped on crank. IT DOES matter where the flywheel is, it should have marks indicating where.

there is a mark on rubber where wire goes out and with piston 1.5-2mm BTDC line up mark on flyheel. then adj. points, 15-20 thou.

mine slipped because tapered shaft and flywheel were "gauled" and I had to lap them in and tighten the hell out of nut,

wouldn't hurt to clean carb also, I've found you gotta do it at least 3-4 times, those french carbs are a %$&#*

good luck (this is why I drink)


Re: SERIOUS spark issues on a Peugeot 103

How much of the 5 coil system do you have? I was lucky enough to be given many peugeot engines when I got my TSM. One of the engines happened to be a 102sp and I just removed the entire magneto with housing and it mounted directly to the 103 engine.

You know that there is an exterior coil(like most other mopeds) linked to the magneto with the later 5 coil systems, right? I had hoped this would solve ignition problems, because before the switch I was blowing condensors like mad! I never really got a chance to find out since I moved and the 103 went to my parents garage.

When a 103 is running good they really move. Faster that my TSM which irks me......

Blowing condensers?

Ok, hafta ask.. why would a the magneto on a Peugeot 2-coil 'blow' condensors?

I'm an electronic tech, and I know that you don't install a capacitor (condenser) with too low of a voltage rating in a given circuit. Standard ignition condenser value is about 0.20uF, and there is no problem making a 1KV part (or better) in the package size used in a moped.

I'd think that a part with a proper voltage spec would be just fine.. or is there some big defect in the design that lets some insane voltage hit the condenser?

Blowing condensers?

They generally don't blow. Too much heat when soldering them in can cause damage to the plates, and they also lose effectiveness over time.

Re: SERIOUS spark issues on a Peugeot 103

I have the entire thing. It mounts up okay, except the ignition wire will eventually melt the way it ends up being oriented...but then there is also the problem of the flywheel being too thick.

Re: SERIOUS spark issues on a Peugeot 103

Yeah, so, I have the same thing. Its a peugeot 103. It has a two coil system. It ran fine, then one day it wouldn't idle. A few days later, it would run six blocks then start backfiring, lose power and stall. We've replaced the condenser, ignition cap, wire, and plug. I then ordered a new igniton coil from BJ. I thought "Its the last thing to replace so its going to work, right?" Wrong. I have the same symptom. I can get the bike to start, sometimes, but it only produces spark at high RPMs. You pedal fast enough, you can get it to go six blocks. Then it slows down and backfires to a halt.

What I would really like to do is get a CDI ignition system from 1977 Mopeds. They have a Europarts catalog where you can get a whole modern bolt on ignition system for about $200. If anyone has a 5 coil magneto they would be willing to sell, I'm all ears.

Matt, good luck and tell me if you find anything.


Re: SERIOUS spark issues on a Peugeot 103

did the myserious peugeot spark issues ever get cleared up?

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