LCGB Forums

Right, electrical this time.

Fitted an Anthony Tambs AC stator must have been over a year ago now, never had a problem but in my wisdom decided to get one of his new fangled AC high output coil/cdi units that render the low tension coil on the stator redundant in an attempt to make a more reliable system as it draws its power from the lighting coils instead.

Anyway long story short. Out riding after having this fitted for less that 2000 miles, spanking it up a hill and it just dies, at first I thought I’d holed the piston but then noticed that I still had full compression so tested for a spark....nothing, on stripping it down i discovered the pick up was fine but the low tension coil (despite not being conected) was well and truly melted! The stator and inside of the housing was covered in a whitish grey powder, but all the burned out stuff on the lt coil was melted black plastic.

No there is no evidence of any of the coils or pickup rubbing on the flywheel, fitted an old stator i had lying around and its all good again.

Anyone got any idea what has happened??

What happened to the wire that came off the LT coil ? how did you make it safe when not in use ?

Sounds like it shorted out and drew to much current and the "debris" caused the failure.

MickYork wrote:What happened to the wire that came off the LT coil ? how did you make it safe when not in use ?

Sounds like it shorted out and drew to much current and the "debris" caused the failure.

Taped it up out of the way as instructed.

I have a series 3 with one of Anthony Tambs AC CDI,s (the one that takes its power from the lighting coils as yours does)I've done over 1000 miles and never had any trouble so far.This uses a standard AC Indian stator plate and flywheel.I also have a series 2 with an Indian stator plate and flywheel,but I used an Anthony Tambs external pick up and Ducati CDI,this ran ok up to 50mph but past that speed it started to mis-fire.I changed to the Indian pick up on the stator plate and it runs ok.The only thing I can think is there is something wrong with the external pick up.

Scooterdude wrote:

MickYork wrote:What happened to the wire that came off the LT coil ? how did you make it safe when not in use ?

Sounds like it shorted out and drew to much current and the "debris" caused the failure.

Taped it up out of the way as instructed.

Assuming that that instruction means "Isolate the green stator wire terminal (CDI end) with tape"
It could be that because the coil is now effectively open circuit, the peak rise voltage generated within the coil could have exceeded its maximum safe value causing insulation breakdown as often seen with HT coils? The arcing internally will just cook the coil.

Scooterdude wrote:Right, electrical this time.

Fitted an Anthony Tambs AC stator must have been over a year ago now, never had a problem but in my wisdom decided to get one of his new fangled AC high output coil/cdi units that render the low tension coil on the stator redundant in an attempt to make a more reliable system as it draws its power from the lighting coils instead.

Anyway long story short. Out riding after having this fitted for less that 2000 miles, spanking it up a hill and it just dies, at first I thought I’d holed the piston but then noticed that I still had full compression so tested for a spark....nothing, on stripping it down i discovered the pick up was fine but the low tension coil (despite not being conected) was well and truly melted! The stator and inside of the housing was covered in a whitish grey powder, but all the burned out stuff on the lt coil was melted black plastic.

No there is no evidence of any of the coils or pickup rubbing on the flywheel, fitted an old stator i had lying around and its all good again.

Anyone got any idea what has happened??

With the LT coil burning out it must have burnt the wiring for the pick up or lighting coils,other wise it would have carried on running.

Fast n Furious wrote:

Scooterdude wrote:

MickYork wrote:What happened to the wire that came off the LT coil ? how did you make it safe when not in use ?

Sounds like it shorted out and drew to much current and the "debris" caused the failure.

Taped it up out of the way as instructed.

Assuming that that instruction means "Isolate the green stator wire terminal (CDI end) with tape"
It could be that because the coil is now effectively open circuit, the peak rise voltage generated within the coil could have exceeded its maximum safe value causing insulation breakdown as often seen with HT coils? The arcing internally will just cook the coil.

Yes the green wire that comes from the lt coil on the stator, the conection that goes on to one of the two green terminals on the Ducati cdi is the one that was taped up.

But now im wondering if the lt coil needs to dump its current much in the same way as the regulator does when you leave your lights on to avoid it overheating.
I was hoping to leave everything in place so in the event of the new cdi going tits up I could simply reconnect all the wires back on the old Ducati cdi (that is still in place).
As it stands im thinking of getting one of the better vespa/piaggio pick ups and building a stator with that but without a lt coil, the other options are: leave as is and wait for the lt coil on the stator ive fitted to burn out at some point or just go back to the Ducati system and possibly leave the new coil/cdi unit as backup in case the lt coil on the stator goes at some point.

HxPaul wrote:

Scooterdude wrote:Right, electrical this time.

Fitted an Anthony Tambs AC stator must have been over a year ago now, never had a problem but in my wisdom decided to get one of his new fangled AC high output coil/cdi units that render the low tension coil on the stator redundant in an attempt to make a more reliable system as it draws its power from the lighting coils instead.

Anyway long story short. Out riding after having this fitted for less that 2000 miles, spanking it up a hill and it just dies, at first I thought I’d holed the piston but then noticed that I still had full compression so tested for a spark....nothing, on stripping it down i discovered the pick up was fine but the low tension coil (despite not being conected) was well and truly melted! The stator and inside of the housing was covered in a whitish grey powder, but all the burned out stuff on the lt coil was melted black plastic.

No there is no evidence of any of the coils or pickup rubbing on the flywheel, fitted an old stator i had lying around and its all good again.

Anyone got any idea what has happened??

With the LT coil burning out it must have burnt the wiring for the pick up or lighting coils,other wise it would have carried on running.

Right just had another look at the Tambs stator and one of the interconecting wires between the lighting coils has broken, but how i wonder would that cause the lt to melt??

did the LT coil burning out cause the wire to break ?

MickYork wrote:did the LT coil burning out cause the wire to break ?

ive no idea cant see how it could.

Fast n Furious wrote:

Scooterdude wrote:

MickYork wrote:What happened to the wire that came off the LT coil ? how did you make it safe when not in use ?

Sounds like it shorted out and drew to much current and the "debris" caused the failure.

Taped it up out of the way as instructed.

Assuming that that instruction means "Isolate the green stator wire terminal (CDI end) with tape"
It could be that because the coil is now effectively open circuit, the peak rise voltage generated within the coil could have exceeded its maximum safe value causing insulation breakdown as often seen with HT coils? The arcing internally will just cook the coil.

interested in this.
as i understand it Ant Tambs runs his bike with both a dc cdi with external pick up and the original system both in place and switches between the 2, meaning one circuit is open and he doesnt have issues.

Right, i now know what went wrong. When i fitted the Anthony Tambs cdi/coil on wiring it up I inadvertently conected the green wire from the stator instead of the green wire from the kill button, it started fine but ran slightly odd I mentioned it to Anthony and he said I’ll blow something up doing that and to make sure ive got the wires right!
So i blew the lt coil back when i fitted it and now just by coincidence the wiring on the lighting coils has failed rendering the whole stator duff.

My mistake i hold my hands up