Re: Sachs Prima G3 - spark probs, Intermittent or Diminishing spark

Hows it going Bob?

Please tell me that the guy who rewired the ped didnt change it all to black wiring....

Re: Sachs Prima G3 - spark probs, Intermittent or Diminishing spark

Spark City!

My pal who wired up the bike wired the hell out of it and the blue wire became inaccessible without cutting into his handiwork. So I chased the blue wire from the stator to where it became the black/red wire, then I pulled the red/black wire from the rear brake switch and grounded that (in the attached pic, I connected the black/blue wire to a makeshift blue ground wire). Crank, crank, crank and sparkles galore! Thanks for everyone’s input on getting this thing electrified. And thanks a ton to themotorhead to the instructions on how to bypass the brake switch. I now just need to figure out what’s wrong with the brake switch and fix that. Onward!

SachsPrimaG3-brakewirebypass.jpg

Re: Sachs Prima G3 - spark probs, Intermittent or Diminishing spark

> Pacer Racer Wrote:

> -------------------------------------------------------

> Hows it going Bob?

>

> Please tell me that the guy who rewired the ped didnt change it all to

> black wiring....

And sorry to fall off this mssg board for so long. I got swamped with work and was unable to tinker.

I got the engine running for a few seconds (by priming the engine) and was rather excited, to say the least. I guess the float I put in there is restricting the gas flow and I need to tweak that li'l guy.

Thanks again!!!

Re: Sachs Prima G3 - spark probs, Intermittent or Diminishing spark

Cool.

Thank you for following up.

I was begining to wonder what happened.

Re: Sachs Prima G3 - spark probs, Intermittent or Diminishing spark

I was reading through the first page on the edge of my seat almost yelling at the computer GROUND THE GODDAMN BLACK/BLUE WIRE LIKE PACER SAYS.

then I got to page two and could breathe again.

Re: Sachs Prima G3 - spark probs, Intermittent or Diminishing spark

HA! I had read (on this forum) about the brake switch and I was suspect of the li'l fart-knocker, but it didn't make any sense that I would get a little spark and then it'd fade. Seen that if the brake switch was causing a grounding issue, I'd get no spark at all. But what do I know? Shrug. Shoulda trusted my gut as well.

Now, if anyone can tell me how to trouble-shoot and, ultimately, fix the prob, that's be just alroight with me. It'd be super swell, in fact.

Re: Sachs Prima G3 - spark probs, Intermittent or Diminishing spark

I'd just run through with a multimeter, probably just needs to be below a certain resistance. Check out myrons mopeds.

But the best solution has already been suggested - just leave the blue/black grounded and run all your lights off the lighting coil (the way most bikes do and so you never have this sort of problem appear unexpectedly...)

Re: Sachs Prima G3 - spark probs, Intermittent or Diminishing spark

> Bob Ray Wrote:

> -------------------------------------------------------

> Spark City!

>

> My pal who wired up the bike wired the hell out of it and the blue wire

> became inaccessible without cutting into his handiwork. So I chased the

> blue wire from the stator to where it became the black/red wire, then I

should be *Black/blue* becomes black/red at plug. Be sure wires are not crossed. Look at wiring diagram again.

> pulled the red/black wire from the rear brake switch and grounded that

> (in the attached pic, I connected the black/blue wire to a makeshift

> blue ground wire). Crank, crank, crank and sparkles galore! Thanks for

> everyone’s input on getting this thing electrified. And thanks a ton to

> themotorhead to the instructions on how to bypass the brake switch. I

> now just need to figure out what’s wrong with the brake switch and fix

> that. Onward!(edited)

Re: Sachs Prima G3 - spark probs, Intermittent or Diminishing spark

If you can't get it going, dos cycles has nos Bosch ignition that work wonderfully.

Re: Sachs Prima G3 - spark probs, Intermittent or Diminishing spark

> Daniel '' Wrote:

> -------------------------------------------------------

> If you can't get it going, dos cycles has nos Bosch ignition that work

> wonderfully.

He has it going as stated above^^^^

He has spark now as stated above^^^

And a new ignition will do NOTHING if the wiring on the bike is jacked.

Re: Sachs Prima G3 - spark probs, Intermittent or Diminishing spark

> Bob Ray Wrote:

> -------------------------------------------------------

> Spark City!

>

> My pal who wired up the bike wired the hell out of it and the blue wire

> became inaccessible without cutting into his handiwork. So I chased the

> blue wire from the stator to where it became the black/red wire, then I

> pulled the red/black wire from the rear brake switch and grounded that

> (in the attached pic, I connected the black/blue wire to a makeshift

> blue ground wire). Crank, crank, crank and sparkles galore! Thanks for

> everyone’s input on getting this thing electrified. And thanks a ton to

> themotorhead to the instructions on how to bypass the brake switch. I

> now just need to figure out what’s wrong with the brake switch and fix

> that. Onward!

Also, the wiring diagram shows the ground to tail light as brown. How long or far does that Brown wire go from the tail light before it terminates?

Re: Sachs Prima G3 - spark probs, Intermittent or Diminishing spark... and Float

Y'all!!!! The bike is up and running! Still need to re-wire the lights... That is the next task. I'm posting here to once again thank all y'all. And provide an update:

Aside from the wiring issue, I was dealing with the task of replacing the float. It's one of those Bing carbs with the cube-like float (Bing-85-12-104-A). The float itself was damn near impossible to find. When I finally did find a replacement float, bending the clip so that it's work properly was one hell of a task.

If the tabs that connect to the float to the pivot rod were one millimeter too far bent in one direction (upward), the float would not push the needle up far enough to stop the gas flow and the carb would leak continuously. However, fuel would flow into the chamber and the engine would run. Messy as hell, but running.

When I adjusted the angle of the float by bending the tabs downward, the needle was pushed too far up and would cut the gas flow completely. No fuel flowing past the carb at all. On a fresh start attempt, I'd crank and crank but no fuel was getting into the chamber. When I pulled the spark plug to check if fuel was entering the chamber, I found a totally dry spark plug.

So back and forth i went, removing the carb and opening it up and bending the tabs one direction and then the other. But persistence paid off! After many attempts at getting the float tabs bent properly, it finally both stopped leaking AND let fuel through. The sweet spot was a hair's difference from either not-flowing-at-all or leaking everywhere. It was an unbelievably fine detail.

I could not find anyone here on Moped Army with the same issue, I only found one thread on a motorcycle forum (https://thumpertalk.com/forums/topic/779445-help-bikes-not-getting-fuelupdate-got-it-running/) with the problem I was having so I figured I'd share my experience in the hopes of helping others.

This site was helpful in explaining basic float/needle function:

https://www.fix.com/blog/motorcycle-carburetor-float-height-adjustment/

I'm going to create a new post so this float info is available to others who might be facing the same problem. Thanks a TON!

Re: Sachs Prima G3 - spark probs, Intermittent or Diminishing spark

Now back to the wiring issue.

Do any of y'all have any links or diagrams or step-by-step instructions on how to re-wire the bike so the brake light does not kill the engine?

Thanks again!

Re: Sachs Prima G3 - spark probs, Intermittent or Diminishing spark

> Bob Ray Wrote:

> -------------------------------------------------------

> Now back to the wiring issue.

>

> Do any of y'all have any links or diagrams or step-by-step instructions

> on how to re-wire the bike so the brake light does not kill the engine?

>

> Thanks again!

Did you take apart tail light?

Remove lens, then reflector assembly (reflector is part of base insert with sockets inside housing, do not break) You might need to unplug 3 wires on backside if they are too short. Keep track of where they go. Should be markings: T= tail light B= brake light G= ground.

Anyway, when you get this far you will be looking for ceramic white retangular (old school) resistor behind bulbs and reflectors.

Since electricity takes the path of least resistance it lights the brake bulb. If brake bulb is out then that circuit finds ground through that resistor.

There are two versions of that tail light. One with resistor and one without. According to wiring diagram that bike should have came with a resistor in tail light to keep engine from dying. But if someone over the years changed that tail light assembly out, it may have the one without resistor.

Another possibility is the resistor has a faulty ground.

Refer to that wiring diagram I posted earlier^^

Again, there are three ground points in brake circuit:

1.) Through both brake light switches.

2.) When one or both brake light switches are open ground goes through brake bulb.

3.) When one or both switches are open and brake bulb is burned out ground goes through ceramic resistor.(edited)

Re: Sachs Prima G3 - spark probs, Intermittent or Diminishing spark

I’m hoping to get back to the bike in the next few days and tackle the brake/tail light issue. And I will follow themotorhead’s above instructions for the brake/tail light fixture. While I’m at it, I’d like to alter the wiring on the thing so as to avoid this problem in the future. If that is possible.

Questions:

Can I just disconnect the red/black wire that leads to the rear brake switch & brake light from the blue/black wire that connects to the magneto and then plug the red/black into the yellow lighting circuit wire coming from the magneto? Thereby circumventing the ignition kill in the event of a failing bulb or brake switch?

And if I can plug the red/black brake wire into the yellow wire, would it cause any adverse side effects? If I did this and had a bad bulb, would it cause the headlights to go out, for example? Or other problems?

Thanks!

Re: Sachs Prima G3 - spark probs, Intermittent or Diminishing spark

Its difficult to correct a problem when you dont know the root cause. I would investigate first before doing anything else. With everything working correctly and a resistor in place there should be no problems, other than a brake bulb burning out, but it should still run. You have a bad resistor or bad connection somewhere. Bulbs are gonna burn out no matter what from normal use. The magneto coil that fires ignition coil is grounded through brake bulb, when/if bulb burns out the resistor takes over to prevent motor from dying. All three work together in harmony when there are no bad connections or components. How you gonna improve that?

You need to break out a multimeter and do some work checking wiring, grounds, continuity and components. There is a simple fault somewhere and its not in the original design. Hell, who knows, your buddy that wired it for you may have jacked up the wiring/connections somewhere.

Wires are color coded and if you look closely at back of tail light housing there will be three letters embossed for all three wire connections. G=ground T=tail light and S or B for Stop or Brake light.

Transferring the brake lamp circuit to the lighting coil that powers the head lamp/tail lamp will over load the lighting coil.

Fix it right unless youre upgrade the entire bike to12volts.(edited)

Re: Sachs Prima G3 - spark probs, Intermittent or Diminishing spark

Thanks, themotorhead. I’m glad to learn that I should just keep it simple and fix the initial problem.

I took apart the tail/brake light and see no evidence of a resister. Pics attached. Also, both bulbs in the fixture are 12V/6cp (even though they are supposed to be 6V/5W and 6V10W). This is how the bike came to me. Not sure if that is contributing to or is the problem. The tail light lights up when I crank the pedals (after I removed the ground workaround I put in to get the engine running), but the brake light does nothing when I pull the hand brake lever. Also, there’s no spark without the ground workaround.

Do I need to put a resistor in there?

I reckon I should test the rear brake switch (and maybe the front one) as well? I’ll search the forums for info on how to do this, unless anyone here can walk me through it.

I’ve been having a blast riding the bike this last week, but wanna get the lights working so I can have working brake light and ride at night.

Thanks again!!!

SachsPrimaG3-taillightfixture1.jpg
SachsPrimaG3-taillightfixture2.jpg
SachsPrimaG3-taillightfixture3.jpg

Re: Sachs Prima G3 - spark probs, Intermittent or Diminishing spark

I'm guessing that since there seems to be no resister that this is an aftermarket light. Here's a pic of it.

SachsPrimaG3-taillightfixture.jpg

Re: Sachs Prima G3 - spark probs, Intermittent or Diminishing spark

Yes that is not the original tail light for sachs prima3. That is a "superman" tail light named for its shape. Used on Spanish versions of the Puch XK magnum and a couple of other peds.

I suppose you could wire in a resistor but without looking up value I have no clue what size you need. Let me dig one of my Garelli tail lights out and snap some pics. It is the same as what yours should have.

12v bulbs will work although they will be dimmer when lit. Bulbs are not the problem.

You have two problems.

You dont have the resistor to back up a burned out bulb.

And you have a bad ground to OR from the brake bulb.

Go back to much earlier post^^^ when I asked you where the ground wire physically terminates at coming from bulb(look at wiring diagram) If not that then its the ground wire feeding brake bulb. Theres two wires to complete ground through the bulb one coming to it ans one going to fender or chassis. Look under fender and use a multimeter to check connections in the brake bulb curcuit.

You will find it I'm sure.(edited)

Re: Sachs Prima G3 - spark probs, Intermittent or Diminishing spark

Here we go..

I borrowed this pic from another post in repair for convenience....thank you spencerr r.

See that big ass ceramic resistor?

Look close...

Middle wire connection tab is brake or stop connection and will be marked on housing with B or S. Goes through bulb to left wire connection tab (and so does resistor). Left wire connection tab will be marked G for ground and that wire will terminate to fender underneath and thus the curcuit is complete.

Now if that connection is not made or the fender itself is not securely grounded to frame and frame to engine then you will have no ground or you will have an incomplete curcuit. See why a multimeter helps in sorting out connections?

BTW...this pic is up side down and second pic shows the complete tail light called "square" C.E.V tail light. Thats what came on your bike originally. Again, there are two versions of that light one with resistor and one without. Wiring diagram I posted says yours bike had that resistor. Some bikes did not and this adds to confusion becuase peeps are not aware of what applies to one ped may not apply to another.

But at the end of the day the tail light to have is the one with the resistor and have it wired correctly so engine does not die when bulb burns out. I'm not an electrition so I dont know what modern day resistor would be a good substitute.

moped-army-e8b2d434e809ab3da93df17502c25b96.jpg
download7.jpeg

(edited)

Re: Sachs Prima G3 - spark probs, Intermittent or Diminishing spark

Ha! Get this: I’m testing the resistance between all connections and everything looks good. Working my way from the back of the bike to the front. Even tested the rear brake switch. All good so far. I get to the front brake switch and there is no ground wire whatsoever! I throw in a quick ground to the front brake and not only am I getting tail light, I am also getting spark! Before that it was an either/or situation. Either spark or tail light.

However, when I pull the brake lever, the brake light does not come on, but the tail light goes off! Weird. But that’s enough for tonight. I’ll take that small victory to bed.

And try to figure out why the hell pulling the brake lever turns off the tail light tomorrow.

This is a big learning experience for me and I appreciate the wisdom and info shared here. Thanks and cheers!

Re: Sachs Prima G3 - spark probs, Intermittent or Diminishing spark

Good deal.

You said you are checking resistance. I am wondering if you meant continuity? Meaning, you are looking for good connections or lack of connections.

Remember, the brake light curcuit uses both the front and back brake light switches that are wired in series. Series means in one single line. When either switch is activated the single line is broken and the brake bulb comes on.

If the tail light goes out when brake light is activated its because tail light has got a bad ground or the ground for the tail light is not wired correctly.

Having that superman tail light wired in could be part of the problem because that light is most likely wired differently within the housing.

Get a square C.e.v. tail light with resistor and put back on the bike when you can.

I did notice more than one blue wire in your photos and that is not original and can add confusion. Again, the multimeter will sort that out and you can label identical color wires for future reference.

Keep up the good work.

I'm here for you.

Chris(edited)

Re: Sachs Prima G3 - spark probs, Intermittent or Diminishing spark

Hello again, gang! I finally went and found the proper tail light and put that sucker on and it runs great! Tail light works, brake light works. I even got the headlights up and running. I couldn't have done it without y'all and I wanna especially thank Chris for hanging in there and helping me at every turn. I really appreciate all the time and energy and good will y'all put forth to help me get to the bottom of this. Cheers to many miles of good riding.

Now I'm off to figure out why the hand brake activates the brake light when the lever is in its resting state and turns OFF the brake light when it's pulled. That's my one remaining hitch. The foot brake activates the brake light when pressure is applied (as it should), but the hand brake lever ain't right. I'm gonna search these forums (thanks, forums!), but if any of y'all know a quick fix, please do tell. Thanks again!

Re: Sachs Prima G3 - spark probs, Intermittent or Diminishing spark

Might have figure it out.

This bike requires an NO (normally open) switch. When in its relaxed state (lever puller; with the button popped up) there should be no continuity. But there is. Maybe there is a NC switch in there?? Unless I don't understand the workings of NO and NC switches (which might be the case), this sounds like the problem.

I'm not an ohm meter expert, but I did a continuity test and when in its relaxed state (lever puller; with the button popped up), there is continuity. With the button depressed, there is no continuity. This is backwards from what it should be.

From: https://www.mopedarmy.com/wiki/Electrical

"N/O and N/C which is normally open and normally closed, this refers to the continuity between the contacts when the switch is at the rest position. ( N/O electricity does not pass when at rest ). ( N/C electricity does pass when at rest) . this can lead to some confusion as at rest can be different when installed. "

Feel free to correct me if I have misunderstood the goings on here. Cheers!

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