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Bike was running well and suddenly died.
Found no spark and narrowed it down to the CDI.
replaced spark plug with new resistor plug , cap and wire
Replaced CDI with a new Ducati brand CDI ( Blue plastic unit) which burned out after after a 2 mile test drive. Bike just died.
Replaced CDI again, this time with a cheap Mitsubhi model.
This bike kicked over easy but died again just going around the block.
This time however , I smelled burning and the CDI started visibly smoking . This happening while i was just walking the bike with the ignition turned on, motor off.
Turned off ignition and the smoke stopped.
Any thoughts or help would be greatly appreciated. Thanks in advance.
Dave
@mjrally avatar
UTC

Veni, Vidi, Posti
73 & 74 Rally, 76 ET3, 80 P200, 06 PX150, 59 Ser 2, 65 Silver Special, 90 V5N 50, 2015 HD Road Glide Special
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Veni, Vidi, Posti
@mjrally avatar
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UTC quote
I'd start looking at the stator and the wiring. What's the history with that? OG? eBay? Never rewired?
@greasy125 avatar
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Sergeant at Arms
Weird 80's Vespas & Cool Vintage Lambrettas
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@greasy125 avatar
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UTC quote
my mind went directly to checking your grounds.

but more than likely you've got a dead short that's back feeding to either a coil in the stator or direct back to the CDI.

since it's present with the key on, that indicates battery power so I'd separate that circuit and select it for testing. pulling the green kill wire would eliminate one possible culprit fairly quickly and then direct your area of search to the stator itself rather than the entire wiring harness (I think).

good luck with the diagnosis and repair!
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Hooked
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Hooked
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Cdi's will burn out if they get a DC feed to them!
Pull the green kill wire off of it and see if this has a DC voltage on it, when the ignition is switched on.
OP
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MJRally wrote:
I'd start looking at the stator and the wiring. What's the history with that? OG? eBay? Never rewired?
A good friend of mine who is a professional scooter mechanic built the bike for me from some left over projects in his shop. Assembled the motor , etc... He says the stator and wiring is original "used" with the motor and looked to be in good condition. Not sure if he tested beyond a visual.
The bike has tested well and run strong with no issues until this ...I am still breaking in the motor at this point.
He also suggested checking the stator , but unfortunately he lives too far from me to service .
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greasy125 wrote:
my mind went directly to checking your grounds.

but more than likely you've got a dead short that's back feeding to either a coil in the stator or direct back to the CDI.

since it's present with the key on, that indicates battery power so I'd separate that circuit and select it for testing. pulling the green kill wire would eliminate one possible culprit fairly quickly and then direct your area of search to the stator itself rather than the entire wiring harness (I think).

good luck with the diagnosis and repair!
Thanks Greasy !, Great advice...This is where I will start... I will try to post an update at the next stage.
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firekdp wrote:
Cdi's will burn out if they get a DC feed to them!
Pull the green kill wire off of it and see if this has a DC voltage on it, when the ignition is switched on.
Thanks Firekdp , I am getting a DC reading of about 2 volts with the switch turned on.
Interestingly, if I turn the handle bars while testing, the volt reading goes up and down.
Maybe a short in the harness somewhere ?
What The? emoticon
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Hooked
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DaveTils wrote:
Maybe a short in the harness somewhere ?
What The? emoticon
Yes, you've got a DC wire coming together with the green somewhere.
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Thanks for all the advice folks ! Its not resolved yet but I tracked down a fried decomposed green wire at the key ignition under the headstock . I'm going to attempt to replace the wiring harness.
Got the tank out and waiting for the parts to arrive.
Any tips and tricks on pulling a new harness through the body would be greatly appreciated.
Either way i will try to post the outcome once I have finished.
Wish me luck !
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Beer and patience, lots of patience.
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63 GL, 76 Super (x2), 74 Primavera (x2), 79 P200, 06 Fly 150
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Haven't done a chemical analysis on it, but the green kill wire on P-series scoots appears to have been made from some blend of cheese or pasta that had an expiration date shortly after leaving the Piaggio factory.

Tape a new wire to the end of a clutch or brake inner cable and fish the new wire through the frame.
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1979 P150X, 1983 P200E, 1987 PK125XL Elestart, 1988 T5, 1995 PX200E, 2011 Yamaha Fazer 600 S2
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@safis avatar
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Green kill wire…
Forum member supplied image with no explanatory text
@hec_in_omaha avatar
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Hooked
1980 P125X US Spec
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Hooked
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UTC quote
DaveTils wrote:
Thanks for all the advice folks ! Its not resolved yet but I tracked down a fried decomposed green wire at the key ignition under the headstock . I'm going to attempt to replace the wiring harness.
Got the tank out and waiting for the parts to arrive.
Any tips and tricks on pulling a new harness through the body would be greatly appreciated.
Either way i will try to post the outcome once I have finished.
Wish me luck !
Take a look at the green wire at the kill switch. Mine was toast there too on my 1980 P125X.

P Series US SPEC Kill Switch Green Wire/Re-Wiring

Hec
Green wire strikes again!
Green wire strikes again!
@subetherbass avatar
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UTC quote
SoCalGuy wrote:
Haven't done a chemical analysis on it, but the green kill wire on P-series scoots appears to have been made from some blend of cheese or pasta that had an expiration date shortly after leaving the Piaggio factory.

Tape a new wire to the end of a clutch or brake inner cable and fish the new wire through the frame.
I agree! Never had such a tasty wire before.
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The green wire on my P was exactly the same. A few wires in the tunnel were chewed by mice.
@subetherbass avatar
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Dear Admin of MV UnCoordinated UnCorporated,


Due to escalating Idjitness can you please install an ADDITIONAL Chandlernan Clock for general use

Hopefully Santa brought lots of Fire Extinguishers, not just the ones who identify a fire, but also the red ones that stop them from growing.


Wishing you a Merry & Safe Xmas

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@moto64 avatar
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Molto Verboso
'64 Motovespa 150S (177) , '65 VBB, '66 Allstate SF, '66 180SS
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Molto Verboso
@moto64 avatar
'64 Motovespa 150S (177) , '65 VBB, '66 Allstate SF, '66 180SS
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UTC quote
DaveTils wrote:
replaced spark plug with new resistor plug , cap and wire

FWIW... you want a resistor plug or cap but not both.
OP
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Update ... problem resolved after running a new green wire and installing a new CDI . Everyone, thank you for all the great suggestions and sharing the knowledge. It is much appreciated.
Installed a new key ignition for good measure.
The only mystery is now is that the kill switch doesn't work, but the key switch does kill the motor.
I'm thinking I missed or crossed some wire in all that garblygook under the headstock.
@ray8 avatar
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Molto Verboso
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Molto Verboso
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DaveTils wrote:
The only mystery is now is that the kill switch doesn't work, but the key switch does kill the motor.
I'm thinking I missed or crossed some wire in all that garblygook under the headstock.
Better
You're more likely to bump it to kill by accident and not know why it isn't starting vs ever use it.
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