MRC Forum- brought to you by www.morini-riders-club.com

Well I rigged up a temporary fuel supply this morning (the tank's still off for painting) and the engine started fairly easily. A bit of carburetter tweaking and now it idles and runs well. No ominous noises. Phew!

But the alternator isn't charging and a quick check shows that it's open circuit, not a good sign. I'll take the cover off yet again later and have a look round - you never know your luck, there may be a wire off or broken or something nice and simple like that. Or maybe not. Can anyone tell me the different alternator types? I remember reading that this model (1978 500W) has a 130W alternator. I think the one on my 1985 350K2 is rated at 120W (not sure about that), but my mental image of the K2 rotor is that it had more poles - is that possible? Maybe I'll have a look at that one as well. One ominous sign is that when I got the bike, the two yellow wires were already disconnected from the regulator.

I'm starting to get the feeling that this bike doesn't want to go back on the road!

Not sure whether to be pleased or disappointed at the moment!

Joe.

Well I had a closer look at the stator coils and of course there's no simple fix. This is what I found:



This coil has been overheating and the wire has broken at the corner of the bobbin. Looking with a magnifying glass, it looks like a single shorted turn, but that turn and the adjacent one look a bit cooked. Needless to say, this is the innermost layer of wire and not easy to fix satisfactorily without re-winding the whole coil. I have considered bringing out that wire and re-terminating it, and that would probably work. It would also probably be unreliable! I did wonder if the regulator had broken down, but both input terminals measure open circuit to earth (apart from a small capacitor) so working or not, it isn't imposing an excessive load.

I'm not sure I understand this stator very well though! Assembled, it looks like this:



There are three short coils and two taller ones. Each coil has two windings which I haven't traced out properly yet. It's difficult to do because the resistances are so low. I've only found one break so far, but all three output wires are open circuit (yellow 1 to red, red to yellow 2 and yellow 1 to yellow 2). I would have expected this to need two breaks, unless I've completely misunderstood it. So, it may not be a case of rewinding one bobbin, there may be another break which I've not yet detected.

Add to this the fact that the magneto winding measures 232 ohms, a bit borderline and I think I need a new stator - has anyone out there got one for sale? Also, anyone got any comments or bright ideas? Thanks!

Regards,
Joe.

Hey Joe

I´m absolut the wrong one to explain any stator But the 232 ohms of the ignicion coil are not that bad tampoco.

norbert

As Norbert says, I wouldn't be worrying about that ignition source coil. I also think you have another trip to NLM coming up or a plea via the wanted ads here. I have a couple of used stators but their condition is suspect. They have been removed due to some failure or other. I think I was keeping them to get rewound some day, something I've never done. NLM used to get them redone by a local firm but I think they are now closed, maybe they have another lined up? If a good rewind firm is known about then I'd like to hear about them as well.

3rd edit. I must be tired!

I'm not too concerned about the magneto coil, as I say it's borderline but it's working fine at the moment. The alternator coils are well within the bounds of a diy re-wind, which at the end of the day is probably what I'll do. I'll sit down with a soldering iron and a meter in the next few days and map out exactly how those 5 coils are wound and interconnected. There must be a second break somewhere, so I need to find that and hopefully I'll just have two coils to re-wind. Of course there is still the question of why they failed......!

I wonder what the next problem's going to be?

Hi Joe,

I believe that Paul C knows quite a lot about the stators. I am with you in wondering what the differences are in the alternators to have such varied outputs quoted and how you can identify them.
Anyone know how to detect a 100W from a 130 or 140W (blue book figures) unit, or is it all in the magnets in the 2 flywheel types?
What I do know is that should you rewind your coils (and why not), be careful not to damage the bobbins as you can't get replacements!

I'll call round and see you soon for my carbs and ignition bits as it is getting close to riding weather again,

George.

PS: As other have said, at 230 ohms, there is nothing wrong with your ignition bobbin.

Can't help with alternator ID, but as George says, why not rewind the coils? I successfully rewound an ignition bobbin some years back, so I imagine a low voltage coil would be much easier. Basically take it apart (carefully), count the turns, measure the diameter and rewind. I can't remember my source of copper wire, but you can buy it with fluxed varnish to make soldering easy. Look at the Dutch club site for the ignition bobbin rewind.

George 350 wrote:Hi Joe,

I believe that Paul C knows quite a lot about the stators. I am with you in wondering what the differences are in the alternators to have such varied outputs quoted and how you can identify them.
Anyone know how to detect a 100W from a 130 or 140W (blue book figures) unit, or is it all in the magnets in the 2 flywheel types?
What I do know is that should you rewind your coils (and why not), be careful not to damage the bobbins as you can't get replacements!

I'll call round and see you soon for my carbs and ignition bits as it is getting close to riding weather again,

George.

PS: As other have said, at 230 ohms, there is nothing wrong with your ignition bobbin.

One of the parts books talks about 3 and 6 magnet rotors. Mine has 6 poles but I'm not quite sure how the actual magnets are arranged, I might see if I can figure that out.

As you can see from my picture, I broke one of the side cheeks off the bobbin I examined, but I think that's easily repairable and the main coil former shoud be OK. Yes, at the moment re-winding looks like my best option, there can't be too many turns on there and I've re-wound plenty of transformers in the past - though not recently!

Yes George, thank you for the loan of the carbs and ignition parts, which I think helped keep evil spirits away on the 500, which has had no ignition problems, so far! I'm a bit embarrassed to have held on to them so long, but they are ready for you - if you'd like me to post them, just say the word.

It was great to have the 500 engine running, it sounded fine and after being a bit reluctant the first time, it now starts easily and it idles well. The "no volts" issue was a bit of an unwelcome bummer though!

Well, I try it:

1. generation (100W): te package of the metal plates for all coils is 11 mm thick, with a red wire (5 wires: 1xred, 1x white, 1xgreen,2x yellow), flywheel without airshovels, regulator that can be opened. As far as I know this flywheel only works with this stator.But probably you can use a more modern flywheel with the first genertion stator. Not sure about that.

2. generation (120W?): also red wire, metal plate pakage 14 mm all (or ignicion coil an one other one still 11 mm), flywheel with airshovels, the same regulator or the ones you cannot open 18A

3 generation (140W?): for example W500 without red wire (only 4 wires: two yellow, the green one for ignicion and a white one that is mass), metal plate packet 14 mm, regulator 18A with B+port, flywheel like second generation 350 but about 1 kg more weight (500)

4. generation (200W?): without plastic corps for the coils, the wire is directly bound on the nucleos, regulator 28A, about 200W, flywheel like 500. The wirng looks like a kid had done it. This alternators you find in the Customs and Camel 501 that still do not have the Kokussan. I supose also the Kanguro X3 has got this strong generator.

That´s what I have written down some years ago, but as I said, I´m an absolute electrolegastenic

saludos
norbert

Norbert, many thanks! This seems like useful information, let me add what I have discovered so far from my alternator, the bike by the way is a 1978 500W.

1. All the laminated cores are 14mm thick.
2. There are 4 wires: Yellow 1 - Yellow 2 - Red - Green. The other side of the ignition coil is grounded to the alternator core.
3. There are fan blades on the flywheel - I like the term "airshovels" by the way!
4. The regulator can be opened by removing two screws.
5. The rotor has 6 pole pieces, 3 North poles and 3 South poles - I am interpreting this as a 3 magnet rotor unless anyone corrects me.

I have found a photo of the stator from my 1985 350K2 and it looks identical. Unfortunately I don't have a photo of the rotor, but I think it had more and smaller pole pieces. I may be wrong, I don't feel like stripping it down to see but maybe curiosity will get the better of me!

I have traced out all the interconnections and coil configuration of the stator, I'll try to draw a more tidy diagram later and post it on here. Advance warning - I'm no draftsman!

Joe.

Ha! I've found a photo of the K2 rotor and I was wrong, it's identical to this one on the 500W, 6 pole pieces.

Well it looks as if re-winding the stator coil should be easy, and I'm just waiting for some wire to arrive. I actually had some which would probably have done, but it was just a little thinner than ideal. The original wire measures 0.9mm over the varnish, so the copper is about 0.85mm. On the taller bobbin, there are two coils of 40 turns each - about 2 layers in each case. The bobbin is only about 2/3 full, so there is plenty of room. Here are a couple of sketches I made, apologies for the quality of my drawing!



This shows the connections on the actual coils. In both cases (tall and short), two of the wires are terminated on eyelets in the end cheek of the bobbin and the other two are just flying leads. I have called them A,B,C and D for the tall coil and W,X,Y and Z for the short coil. The 5 coils are interconnected like this:



If you trace that out, you'll see that one coil on each bobbin is connected in series (5 coils) to form one output (yellow wire) and the other 5 make the other output. One end of each string is common and connected to the red. This makes the two outputs out of phase, so I'm guessing the regulator incorporates a "full-wave" rectifier, 2 diodes.

All this is incidental though, all I have to do it wind two coils of 40 turns each! I'll let you know how I get on.

By the way, I think the root cause of all this was a shorted turn. The overheating is very localised and only affects about two turns on one layer.

Joe.

Interesting. I have just repaired my stator form the 6 speed 500, I could only get a voltage from one yellow wire and open circuit on the other which was traced to a broken wire from one of the bobbins. I am lucky in that I had spare bobbins from a smashed stator - crankshaft had snapped. These drawings or similar and the wiring diagrams were done back in the early eighties and featured in the club magazine. The chap who's name escapes me went into great detail on the electrical output and the ignition operation, I sold off almost the complete set of magazines last year, so if the club has a library then these articles should be printed again for reference they are most interesting.

If you begin to wind up some coils, maybe it´s worth thinking of widing them all new to convert it in a stator without red wire (using bobbins with broken wire from any failing startor, if you can). Then probably yo´ll need another regulator,but you´ll have some more watts! Don´t ask me how to do. But surely all this is said in the articles mentioned by Harry

norbert

Hi Norbert,
Haha! Now you've got me thinking! That's a very good idea, re-wind all the coils as a single winding alternator and use one of the many modern single phase regulators available. Of course I don't know if the original regulator works or not anyway, and one thing for sure, it's 40 years old! I'll give it some thought. Hmm, the easy option is just to rewind the one coil and see how it works. I have no spare bobbins, so if I decide on a complete rewind, it's a one-way trip!

Watch this space!
Joe.

That´s also the way to pimp the electric/stator of the older enduros to 12 V. And as you said, there are much more regulators available for little money.

norbert