Low Tension Coil

[jonno]

Just a few questions ..
Is there any way of finding out if the low tension coil is on the way out ? Is it by the readings from the red white and green wires ?
When the coil goes are there any other parts on the stator that need replacing as well ?
What causes the coil to break down,can any other electrical part/combination contribute to its demise ?

[Adam_Winstone]

You need to get hold of a multimeter and measure the resistance between the stator’s white and green wires, which should return a figure of about 400 ohms. You can get additional info on testing from various places, incl. Cambridge Lambretta’s website, Sticky’ Manual, etc.

http://www.lambretta.co.uk/downloads/el ... cprobs.pdf

LT coil failure is all too common and something that many have suffered. It doesn’t seem to be exacerbated by other components and typically nothing else will need replacing. One thing to watch out for is that some failing LT coils still give reasonable resistance figures and sometimes perfectly good stators can give low readings so even multimeter testing might not identify a problem. This does,however, mean that substitution for a known good stator is a very good test of the stator in general.

If multimeter testing does give you a low reading then your options are to replace the LT (if your soldering is good), upgrading to a better LT coil (Indian stators have an LT of one size, Italian and BGM use another... they are not interchangeable without modifying the stator plate), replacing the stator (various options but some are likely to suffer LT failure again) or even a new option of replacing the coil with a new CDI that sources it’s power from the lighting circuit (it doesn’t matter if your LT has failed.. not that these have just been developed and have yet to prove themselves long-term, now available from Readspeed). As such solutions range from about £10 (Indian LT coil), upgrade coil (£20-30 ish, Indian stators needing modification to use them), stator replacement £35-100, change to new lighting circuit CDI (price unknown but I believe they are now on sale. Lots of options to choose from.

My personal experience, and speaking as someone who too often fixes failed stators for others, is that replacing a failed LT with another cheap LT typically leads to failure again. Many people in my club have had very good reliability from use of the BGM stators. Anthony Tambs (do a search) is producing a stator that is getting good reports. I’ve been lucky enough to trial one of Readspeed’s new CDIs and can confirm that they do work but even I must acknowledge that this is a new product and I’ll want 5000 miles under my belt before I can even start to comment on reliability! Also don’t forget that others have made a complete swap to other systems (e.g. Varitronic, etc.) to get away from the common reliability issues (other features besides)that many suffer from cheap electronic kits. However............. my ‘go to’ fix, which has proven its worth time and time again is an upgrade to a better LT coil (there is an upgrade thread on one of the forums).

Good luck, whichever way you decide to go... and, yes, testing is your first step.

Adam

[jonno]

Thanks Adam Ive had a BGM coil go and looking to fix it with BGM parts. My current Indian stator has all good readings using a multimeter,although Ive had the engine running like sh@t,and no amount of card alterations have made a difference. This set up did run fine last year.

[Adam_Winstone]

I've fitted a number of BGM LTs for people to fix failed SIL LTs and to date, I don't think that we've had a BGM stator or LT fail in our club... but have done thousands of reliable miles on them. That said I have noted a few such reports from others, which might simply be a reflection of how many BGM stators are out there. Whilst I have no personal reason to think that the BGM LTs are not first class, I've spent decades pinching LT coils off genuine Vespa stators (NB: not the multitude of aftermarket Vespa stators now available, which are no better than aftermarket Indian Lambretta stators) and then found that the Italian Ceab LT coils are every bit as good as the genuine Vespa PX/PK/T5 ones. These Ceab ones are not cheap but they typically return a level of ignition reliability that is every bit as good as any Vespa Ducati stator that you might come across (incl. the 80s AF stators). If you hunt around you can find these Ceab LTs at reasonable prices and I personally think that they are worth every penny... typically fit and forget!

It might be worth you borrowing a known stator from someone so that you could confirm whether your current woes are stator related. A good pal of mine spent a long time trying to resolve what he thought to be a carburation, air leak or wiring issue when his bike became very temperamental. He'd checked the resistance figures of his Indian stator and all seemed fine so had discounted this as being a possible cause. Eventually he swapped for a known working stator from another bike and all was fine. He then provided me with the Indian stator and a PX donor, with me modifying the stator to accept the PX LT coils and this was then refitted to the same machine and has worked well ever since. This just goes to show that even when a stator returns the correct readings that it may still be at fault.

I once had an issue with an 80s AF that gave the correct readings at rest, however, there was a tiny break in the LT's wire to earth and this would cause an intermittent misfire when running. Test at rest and all was fine This too was a case of find the fault, resolder, epoxy secure against vibration fracture and not had a problem since.

Stators... great when sorted but a real pain in the bum when they give issue, hence me liking to resolve it once and once only!

Good luck getting this resolved.

Adam

[Norrie Bodge]

whos goin down this route here ?

https://www.scooterlab.uk/new-lukas-cdi ... woes-news/

[Phil D]

whos goin down this route here ?

https://www.scooterlab.uk/new-lukas-cdi ... woes-news/

Might be worth putting in toolbox as back up .???

[coaster]

whos goin down this route here ?

https://www.scooterlab.uk/new-lukas-cdi ... woes-news/

I would hazard a guess that that is a DC ignition taking its power from the lighting circuit. Anthony Tambs has one via his Scootronics FB page....I think its about half the cost of the Readspeed one.

[Scooterlam]

if it is DC, would it not need a dc feed rather than the ac most of us would have.
The article needs a bit more meat on the bones.
Ive gone down the ant Tambs route a stand alone system when used with a battery and his external pick up.
wish I had down it before last years euro which ended with replacing a failed stator in a thunderstorm only to find the spare had developed a fault and wouldn't rev. 12 hrs in total and a 50k cab ride back where I came from.
could have been as easy as swithing a couple of wires.

[Knowledge]

if it is DC, would it not need a dc feed rather than the ac most of us would have.

SL,

Have you got an unnecessary NOT in your first sentence? I would think a DC ignition system MUST have a DC feed.

[coaster]

if it is DC, would it not need a dc feed rather than the ac most of us would have.

SL,

Have you got an unnecessary NOT in your first sentence? I would think a DC ignition system MUST have a DC feed.

I believe the DC is rectified from the lighting feed and apparently results in a better spark for starting...better still if you have a battery wired in

[dickie]

it's becoming increasingly common to find kit that will work with either ac or dc.

if you rectify ac you end up with dc. if you rectify dc you end up with dc. in the old days when you had to use a transformer to get the correct voltage that made things tricky but with pulse width modulation and switch mode power supplies, things got easier.

[coaster]

it's becoming increasingly common to find kit that will work with either ac or dc.

if you rectify ac you end up with dc. if you rectify dc you end up with dc. in the old days when you had to use a transformer to get the correct voltage that made things tricky but with pulse width modulation and switch mode power supplies, things got easier.

They didn't transform anything Dickie, the old 6 volt systems has a 12v speedo bulb which was supposed to soak up any excess voltage. This was ok ish for Li's and the like but tuned motors would blow their bulbs and that is why after market zenor diodes were recommended in the Lambretta Tuning Manual.

[Fast n Furious]

The 12V speedo bulb hasn't got the minerals to act as ballast. It was primarily specified to limit the brilliance of the speedo face at night so it wasn't too irritating for the rider.

[jonno]

Is there another washer under the metal retaining plate holding the coil on? Seemed to be a plastic one all disintergrated when I took the coil off.

[HxPaul]

I think thats an anti-vibration washer,shown here on the left. https://www.beedspeed.com/electronic-st ... rtnbag27u5

[jonno]

Does that go under the retaining plate or does it go on before the coil ? I didnt get anything else with the coil when I ordered it.

[HxPaul]

Does that go under the retaining plate or does it go on before the coil ? I didnt get anything else with the coil when I ordered it.

The coil goes on first and then the anti-vibration washer
http://www.ebay.co.uk/itm/Lambretta-12- ... SwaG9XIvj7