Motobecane question for smart people

Does anyone know the difference electrically between the 12v and the 6v systems? I have two engines and from what I can tell the 12v doesn't use the diode that is on the 6v system (usually mounted behind the headlight.). Anyone ever taken apart both? Anybody??? I would like to use the 12v but the bike is 1977.

Re: Motobecane question for smart people

Allen Rinch /

yes.

Re: Motobecane question for smart people

"Yes" I guess means that it will work fine just by taking the diode out of the equation?

Re: Motobecane question for smart people

InfectedBootSector /

No way man. The diode doesn't nes. have anything to do with the voltage. All it does is make sure the flow of current only goes in one direction.

The generator itself is what is putting out 6 volts.

Re: Motobecane question for smart people

I understand that too, but there isn't a diode on the 12v wiring digram. The bulbs and the horn shouldn't care about a different voltage as this goes up and down, but, what about the coil? I have one for the 12v that looks exactly the same. I just can't tell what I would have to change. So far it looks like I just pull the diode.

Re: Motobecane question for smart people

InfectedBootSector /

Actually, your horn and bulbs are both made to work on 6v. If you run the stuff at 12, you'll blow the bulbs and fry your horn.

The Coil won't make the voltage difference except on your ignition. It's all in the generator. The coil is just there to boost the voltage up for ignition.

Re: Motobecane question for smart people

hmm, are you sure, it just doesn't seem like it would make an electrical difference. I believe you though. I wish I could see the different parts. Well I will just try it with 6v. How often do you see magnetos go out?

Re: Motobecane question for smart people

InfectedBootSector /

Yea.. there is a difference internally... so ya can't see 'em.

I'lll see if I can come up with a way to boost the voltage to 12 if I can figure out how to do it on my Puch.

As far as magnetos go.. it is really hard to say. My Puch has the original and it does great, even though it was made in 1978.

Re: Motobecane question for smart people

Yeah, thanks, and it's not a question of which is better, I would stay as "stock" as possible. I just have two and am still putting all the pieces back together after my rebuild. I don't know if the original stuff works yet. The engine is mechanically sound but the last guy crashed pretty hard. So who knows. I figure the bulbs could be changes to 12 volts and it is just a matter of rewiring the rest.

Re: Motobecane question for smart people

Sounds one maybe for Ron Brown.

Your light bulbs on the 1977 would all be 6 volt. It could also affect your High tension coil unless you swap out the 6 volt coil for a 12v.

The diode does control the flow of current to be in one direction but it's main function is to convert AC (from the magneto) to DC (to trickle charge the battery when the engine is running)

Are you thinking about swapping engines? Does the 12 volt have a CDI ignition?

Re: Motobecane question for smart people

InfectedBootSector /

S**t... I forgot to ask if he had a battery or not... hehe...

I always assume they don't for some reason because my Puch doesn't have one...

Re: Motobecane question for smart people

I don't think it is cdi because I think Capacitive discharge uses a battery. I don't have a battary, just my legs and lots of beer...But the diode makes sense as far as lights are concerned. That's the basis of the whole question: what to change. Now I know electricity works different on a 6 volt system and has to be converted but I don't know what happens when it is 12v. The manual is a pitifully translated piece of crap that tells you nothing. Most of the things on my moped are different than the manual says they are. Fun. I took it completely apart anyway.

Re: Motobecane question for smart people

can we not say shit here?

Re: Motobecane question for smart people

SHIT!

Re: Motobecane question for smart people

Ron Brown /

KC,

I am still in Texas and do not have my manual, but as near as I can remember, the diode is a 6volt zener to protect the bulbs from over voltage. The 12 volt system is only capable of putting out 12v as long as all the bulbs are working. Disconnect the dioide and replace all the bulbs with the correct 12 volt and you should be ok. The horn may be unhappy at 12 volts but unless you lean on the button I don't think it will burn out. It may make your brake lamp really dim.

The ignition uses a separate coil in the mag and is most likely the same in 6 and 12v peds. Check one of the ped shops and see if they both use the same replacement coil.

Ron

Re: Motobecane question for smart people

Ron is exactly right. There are three coils in the mag. One is for ignition, one for power and the other I guess supports the power (maybe another 6v mag [6 + 6 = 12]). Does that mean it is DC and is a generator? Contrasted with the 6v AC that has to be rectified? How and why you are so smart I dunno. Years of 2 stroke fumes I suppose.... I will update everyone if it works. Just so you can laugh if I screw up > then I'll say shit again, maybe even the F word.

Re: Motobecane question for smart people

Ron Brown /

KC wrote:

>

> Ron is exactly right. There are three coils in the mag. One

> is for ignition, one for power and the other I guess supports

> the power (maybe another 6v mag [6 + 6 = 12]). Does that

> mean it is DC and is a generator? Contrasted with the 6v AC

> that has to be rectified? How and why you are so smart I

> dunno. Years of 2 stroke fumes I suppose.... I will update

> everyone if it works. Just so you can laugh if I screw up >

> then I'll say shit again, maybe even the F word.

KC

Probably Castrol R.

I don't think you can hook the coils in series for 12 volts because they are not phased correctly to do that.

One of the coils is for head/tail/instruments, the other is for stop/horn. Both are ac coils. The diode is a zener diode which is a voltage regulator, not a rectifier. It clips the ac if it exeeds 6 volts, sort of like a lamp dimmer in your house. You must remove it if you switch to 12 volts.

Ron

Re: Motobecane question for smart people

Yeah the bean oil stuff is smelly.

Thanks again Ron, everything you said makes complete sense. Not rectified but regulated - that is the opposite of what I thought it was for. I have the 12v coil so I will use that. It doesn't seem to be marked differently but I am gonna check to make sure.

kc

Re: Motobecane question for smart people

Actually, the diode is a Zener, and is used for voltage regulation.

Re: Motobecane question for smart people

I hit send before I was done. I have never checked the magneto voltage between pre Jan 78 models and the newer ones, but my feeling is that the magnetos produce the same voltage.

In the 6v system, a Zener diode regulates this voltage to 6v, shunting the excess back to ground. The 12v system just runs at 12 volts without the zener regulation.

I have a 12v July '78 Moby 50V with a pre-78 lower end (and magneto) and I had to modify nothing since the wiring on the bike never had the diode to begin with. The 12v bulbs run just fine. The magneto wires were a different color, but you can mix and match or use a VOM to find the right ones to connect.

You should have no trouble going the other route since your 77 bike already has the diode installed. The 77 is set up for 6v, and the diode will simply regulate the voltage at that level.

See what voltage your machine runs on (check the bulbs) and make certain the diode is installed, if needed. If you need to install the diode, go to any electronics store or www.digikey.com and order a 6v zener diode with a 50 volt rating that will carry at least 2 amps. The diodes cathode (end with the stripe) connects to the black wire behind the headlight, and the opposite end (anode) connects to ground.

Re: Motobecane question for smart people

You seem to know quite a bit about electronics Ron, which is the failing of most mechanics.

You are also very correct. Rectifiers are wired in series with the voltage source, while diode regulators are wired in parallel.

A newer and superior way to regulate is the IC regulator which has three connections instead of the diode's two; an input, ground and output. It has the advantage of shutting off instead of burning up in a thermal runaway situation, and will turn itself back on after cooling for a spell. It is also heat sinkable, and can carry more load for longer periods without failing.

Re: Motobecane question for smart people

I have a moby-motobecane, I bought it and was told the coil was bad. I put a new one on and cant get it running. Can anyone help, or I will sell for 100$

Re: Motobecane question for smart people

Ron Brown /

Dan,

If it is in good shape, you will get all kins of takers on this site at that price.

If you want to try to fix it, go to Resources, Articles and read Fred's "How to fix your moped".

Ron

Sell it to me.

Ron! Doggone you.I was just about to rip him off!Remember I had that Moby I rued getting rid of?Have a heart,man!...............................HEY,DAN-DEE:...WHERE ARE YOU LOCATED? I'll take that no-good `ped off your hands! Don

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