Why is lambretta ignition so unreliable?

[dickie]

A tired and some might think, boring subject. But it strikes me as weird that i never hear of ignition problems on cars or motorbikes. And like most on here, I've had dozens of both, and so have my friends and family. NOBODY starts a journey wondering if they'll make it without replacing a stator, cdi or coil. So what is it that makes them so crap?

I think the low tension coil is fairly easy to answer. It has many turns of fine wire in a hight vibration environment, so it gets rattled to the point that either the wire or insulation breaks. Please correct me if I'm wrong here.

The pick-up is less obvious to me as i don't know what it's made up of.

I've been running DC ignition (like you have on your car, motorbike etc) for several years without issue, but I'm a low mileage rider, so not a brilliant source for reliability data. I also use an external pick up, in the assumption that it's the same technology as used in most motor vehicles.

Maybe I've got the holy grail of lambretta ignitions or maybe I'm just lucky that i don't put the miles in?

Thoughts? Particularly about the difference between external and internal pick ups.

[Fast n Furious]

The notoriously unreliable LT coils on lambretta CDI ignitions can be re-engineered to be made reliable and trustworthy. On my own scoots tho, I just prefer to go DC with the addition of a TV175 DC ignition switch to make it like any other modern motorcycle. (MB now offer a remake of this type of switch.)
On AC scoots, the easiest way to deal with this issue is to fit a Reedspeed combination CDI/regulator. These don't use the LT coil. They use power from the lighting coils instead to generate power for the ignition spark. These work really well and give a great spark from kickstart speed and onwards.
Pick-up coils are usually very reliable but can and do suffer from erratic triggering if misaligned or are subject to a worn mag bearing. All too often the pickup gets the blame here instead of other surrounding issues that have an affect on it!
Externally mounted reluctance sensors can also suffer the same fate as internal ones for the same reasons. Hall effect pickups require the fitting of a small magnet somewhere on the flywheel to trigger the ignition and it also requires a compatible ignition box. Optical pickup triggers are really good but can be a real pain to engineer in, and again, requires a compatible ignition box. In these 2 cases however, the use of Inductive ignitions can be considered (TCI) which offer better performance over CDI on very high reving engines.
These days, multimeter oscilloscope combination meters are very affordable. These are great for analysing the signal ouput from the trigger sensor. A worthwhile investment for all aspects of scooter electrical maintenance.

[dickie]

Pete, thanks for that informed response.

Why do you say that pick-ups are wrongly blamed? I know that in this sort of diagnosis, a lot of guesswork takes place and in the end the wrong thing is disgnosed among a pile of parts changed just to check. But, there does seem to be a good number of BGM ones failing at the moment.

I'm curious as to what a pick up actually is though? Is it just a coil, or what?

Interesting what you say about Reedspeed CDIs having a strong spark at kickover. My DC ignition is weak on kickover as it also has to charge a 10000 microfarad capacitor that i have on the DC output. I tried putting a 13V power supply on to mimic a battery and the difference was amazing. I don't want to fit a switch, just so that i can keep original looks, so I'm building a little PCB to hide inside the junction box. But i also need to find somewhere to hide a small battery. The smallest i can find is 1.2Ah alarm battery.

[L111amo]

Got a bgm stator on my gp, been on for 14 years, never missed a beat, IOW 7 times, Trance 2 times & Belgium once pls loads of the usual rallies, Donno if I’m just lucky, wished I hadn’t said anything now

[Fast n Furious]

Got a bgm stator on my gp, been on for 14 years, never missed a beat, IOW 7 times, Trance 2 times & Belgium once pls loads of the usual rallies, Donno if I’m just lucky, wished I hadn’t said anything now

LT coil failure is a common and well lamented topic.
Like any other known weak point, in any machine, it will likely only afflict the percentage known as the unlucky barstards and I've seen my fair share of these poor saps, usually stranded at the roadside for hours on end.
If only one of you within your riding party carries a Reedspeed CDI/regulator, as a spare, then it would likely cover everyone in the party should the need arise.
Potential brownie points to be had there eh?
It's kinda like...... riding with tubeless tyres and no spare wheel or tyre slime and hoping like f*** you never get a puncture.
Stay lucky.

[Fast n Furious]

Pete, thanks for that informed response.

Why do you say that pick-ups are wrongly blamed? I know that in this sort of diagnosis, a lot of guesswork takes place and in the end the wrong thing is disgnosed among a pile of parts changed just to check. But, there does seem to be a good number of BGM ones failing at the moment.

I'm curious as to what a pick up actually is though? Is it just a coil, or what?

Interesting what you say about Reedspeed CDIs having a strong spark at kickover. My DC ignition is weak on kickover as it also has to charge a 10000 microfarad capacitor that i have on the DC output. I tried putting a 13V power supply on to mimic a battery and the difference was amazing. I don't want to fit a switch, just so that i can keep original looks, so I'm building a little PCB to hide inside the junction box. But i also need to find somewhere to hide a small battery. The smallest i can find is 1.2Ah alarm battery.

Hi Rich,
The switch I was on about is a genuine looking and operating switch that replaces your existing ignition switch. These were a common fitment on ser2 and ser3 TV175's. The only difference is that these switches have an extra wire(white).
The white connects with the grey wire on key positions 1,2 & 3 and is open circuit on positions 0 & -1
You would likely need an extra wire down from the headset to the rear of the scoot to then feed this switched DC to your CDI and any other auxiliaries at the rear.
DC CDI's have a small in-built "switched mode power supply" which converts your 12vDC to 200vDC for the discharge capacitor. (This is the bit that in effect replaces the LT coil on AC CDI's)
An SMPS relies on a specific start up proceedure to get it to work. One part of that procedure is relying on the how the power is applied to it. If yours is relying on the capacitor to charge up as you kick it over, then the voltage to the device will rise up slowly rather than at the normal near instant expectation from a switched battery. This can cause the voltage converter to simply not start up or burn out the MoSFET rendering your CDI as dead.
I have a similar set up on one of mine and if I forget to discharge the huge 2 Farad capacitors by turning the lights on and off before removing the keys, then the caps are left to slowly discharge through my programmable CDI which usually results in corrupting the program's RAM memory meaning I've got to re-program it again. (This will get fixed on its next makeover)
The pickup sensor on a standard stator works similarly to all the other coils on there. There are 2 adjacent magnet poles on the flywheel that have extended lamination legs which cross over each other. The first leg induces a positive voltage (5v) in the pick-up coil which then very quicky turns to -5v as the adjacent leg passes over. The coil of wire is the only thing that can go wrong. The output voltage is proportinal to the air gap between the sensor pole and the passing magnets.
Very often with external pickups the magnet is built into the sensor and these don't need a magnet on the flywheel but do need a raised ferrous peg that the end of the sensor's pole can see once every revolution on a single cylinder engine. These are known as variable reluctance sensors. The +/- output is more or less the same.
I use alarm batteries on mine. Love em cos they can be mounted quite descreetly in any position except upside down.
Cuppa tea needed.

[Scooterslag]

To me - the arrival of the AF electronic kit ( DC and AC) in the 80's seem to be a pretty reliable fit and forget solution to people's electrical woes. For the last 15 years or so though - electronic kits of all makes just seem such a lottery when it comes to reliability . Dodgy pick-ups, flywheels etc. Why has this changed? Cheers Paul

[dickie]

So, I think we have 2 fundamental problems here.

1- Quality. It's a boring and unsurprising conclusion but from what I've seen and scooterslag/F&F's comments, it just seems like LT coils and pick ups are poorly made and installed.

2- LT coils seem inherently weak due to the fine wire used and possibly the type of insulation between the windings as well.

Both F&F and I have moved away from separate stator windings and toward using the lighting coils for ignition and lighting supplies like most vehicles on the planet. His system is better than mine for starting, but both about the same once running. A battery helps a lot here, so I'll be fitting one.

I'm reluctant to say this, but I do think this is the answer to ignition woes on our old shopping bikes. It's also much easier to understand.

It really puzzles me why this type of system isn't being marketed instead of Varitronic etc.

[Rich Oswald]

Interesting thread this because I have found the older Indian kits to be far more reliable than ANY of the modern kits marketed these days. For instance, my GP has has the same Indian electronic ignition kit on since it was built by Sean Burns in 1997 and has only had the CDI changed a couple of years ago.
A previous scooter I owned, I changed to electronic 12v with an Indian kit from Beedspeed in 1998 and that was also fine until it failed and I had it changed around 3 years ago. I have never ever had any other stator problems on any scooter.

I am no expert on electrics but we must ask the question, "what has changed"? Are modern parts that are used much cheaper and more susceptible to failure than they used to be? I find it hard to believe that the Indians were using much better components than we are now!

[dickie]

Rich, interesting history. It shows one of the 2 problems perfectly; poor quality parts. Recent well publicised failures of a make known for high quality are great examples of poor quality. Could someone make LT coils and pick-ups of the same standard now?

It wouldn't be too difficult to analyse the failure modes of pick ups and LT coils if you had maybe 20 failed units.

Once that were known, the solution isn't usually very far away and it sounds like 1990s India had it sussed anyway.

And always nice to hear mention of Sean even though he did make a shit cuppa; too much milk every time.

[Rich Oswald]

And always nice to hear mention of Sean even though he did make a shit cuppa; too much milk every time.

Oh yes, very true. Builders tea for me always!

Rich'

[gaz_powell]

When AF stopped doing the ducati electric kit, SR started offering a geniune SIL kit... SiL stator rewired by SR to vespa colours, a genuine SIL flywheel, ducati cdi and regulator. SR skimmed the long fins to standard height... mines been in for over 25yrs and been used.
Flywheel has been lightened since original installed and its been rewired as the cables got hard.. Still has same pick up and LT and has had one cdi change (replaced with ducati).
The engines had three cranks, several bearing replacements and its in its second TS top end.

Several years later another build same kit from SR.... Thats had 1 pick, 1 LT and a regulator swap, in 20yrs and its been well used. The failures in last 5 yrs.. And one rewire. Engines had three lits of bearing through it.

Those first kits as said were spot on.

I still use genuine SIL stators and flywheels with ducati cdi and regulators.... Wont change, last pick up and LT swaps were genuine piaggio still going strong.

This post will be the ultimate kiss of death!!!

[dickie]

When AF stopped doing the ducati electric kit, SR started offering a geniune SIL kit... SiL stator rewired by SR to vespa colours, a genuine SIL flywheel, ducati cdi and regulator. SR skimmed the long fins to standard height... mines been in for over 25yrs and been used.
Flywheel has been lightened since original installed and its been rewired as the cables got hard.. Still has same pick up and LT and has had one cdi change (replaced with ducati).
The engines had three cranks, several bearing replacements and its in its second TS top end.

Several years later another build same kit from SR.... Thats had 1 pick, 1 LT and a regulator swap, in 20yrs and its been well used. The failures in last 5 yrs.. And one rewire. Engines had three lits of bearing through it.

Those first kits as said were spot on.

I still use genuine SIL stators and flywheels with ducati cdi and regulators.... Wont change, last pick up and LT swaps were genuine piaggio still going strong.

This post will be the ultimate kiss of death!!!

Well, more evidence that quality has gone downhill! Those numbers look good in comparison to Lambrettas but they're pretty poor compared to cars/bikes in general. I'm presuming you dont do 10,000 miles per year here.

That said, I'd be happy with that level of reliability, especially for the low miles that I do.

It's hard to say if what I run is better than yours as the CDI in particular has very little data. And if I get a good one, say for a honda, it will almost certainly have an advance curve built in, which is the opposite of what we want. Personally, I prefer static timing.

Maybe I should spend some time trawling t'interweb for static CDIs?

[Adam_Winstone]

My old Audi A4 had the Bosch CDI pack up, which was replaced in other countries as a recall item but not in the UK. When you ordered the same Bosch replacement part, you received the Far Eastern replacement part that had been sent out free elsewhere. Just goes to show that European doesn't always equate to quality and that it's not just our ignitions failing.

Back to Lambretta - Yes, it's typically the failure of sub-standard LT coils or pickups that cause traditional 12v electronic ignitions to fail. Older genuine Ducati parts are commonly still working now!

It's not a Vespa vs Lambretta thing either as most of the aftermarket Vespa stators are just as unreliable, whereas original Ducati are great.

Happy & reliable riding to you all.