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Ignition Problems LD's

Technical help for all early models, A, B, C, LC, D, LD, E & F models

Ignition Problems LD's

Postby JLD1 » Sun Apr 12, 2020 1:42 pm

Hi All, I am hoping someone may be able to help with some questions please?

I have a few LD's. I am trying to fault diagnose starting problems with one and have a few questions. In summary:

Lambretta 1 - Not working
Condensor Capacitor replaced.
Points replaced, although they seemed OK!
Stator plate status for starting and timing - probably out of alignment as I have never got this one started. I have moved it to various positions and can play with this further once I get a spark.
Ignition coil - Unknown about the state. looks OK, but testing seem impossible for these.
Lighting coil - Unknown about the state. looks OK, but testing seem impossible for these.
Flywheel Magnetic strength - Seems OK as far as I can tell and when compared to a working LD
External HT Coil - Not installed yet

Summary - I am unable to get a spark from the green cable / or electric shock if holding it. My next step is to start replacing the Ignition & Lighting coils with working ones from another LD, which I would like to avoid doing, unless anyone else has any thoughts or ideas on how to test these further or fault diagnose? However, before I do so, the Lambretta I am about to strip it with (is up and running and all is fine!) is displaying the following problems

Lambretta 2 - Working OK. However, I have no spark from green wire or electric shock if I hold the cable?. I'm using a external HT Coil for this one.
This LD Lambretta starts and is fine. It uses an Italian H.T. Coil (Green cable to HT Coil, then HT lead to spark plug). When disconnecting the external HT coil and testing the green (or the lighting / brown) cable coming out of / from the LT terminal (AKA connection block) , I do not get a spark, nor do I get an electric shock if I hold it in my fingers. However, once I attach the green cable to the external H.T. Coil, it starts with no problems. Might it be a case that I'm simply not kicking the kick start leaver hard enough to get a spark / electric shock from the green cable, or am I missing something? Normally I don't have to provide much effort to get a small spark or electric shock, but to get nothing at start it up with a slightly hard kick (Which I am doing when holding the green cable) is a mystery? This one normally starts after one or two kicks.

Condensor / Capacitor Question
Is three any difference between Filso and Marelli condensor capacitor and if so, what is it? I am currently using the correct one. However, I can buy Filso ones online with x2 cables required coming off it. Marelli ones, you need to solder the cables and my soldering needs improvement, so I am wondering if they are interchangeable, or must I use Filso for Filso and Marelli for Marelli and if so - why? Anyone know the difference?

Lastly - Stator Plate Alignment to begin with
Has anyone any tips on Stator plate installs for a new LD build that's in bits, or is it a simple case of installing it and moving it gradually, until it backfires, then starts and then go through setting up the timing process? This is how I rebuild them at the moment (going through a few woodruff keys sometimes), but I'm wondering if there is an easier way?

Any comments, thoughts or advice would be gratefully received.

Thanks for reading.
JLD1
 
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Re: Ignition Problems LD's

Postby jbcollier » Wed Apr 15, 2020 4:08 pm

The only reason to change points is if the contact surfaces are pitted or burnt. The contacts can get dirty or oxidized. In which case I use clean white paper pulled between the closed contacts to clean them. Make sure you lightly apply grease to the points cam so your adjustments last as long as possible.

Condensers are the most common failure and they can be bad right out of the box.

The voltages generated in the green wire are not very high and will not produce a spark or give a shock. The external ignition coil is the voltage multiplier which generates the spark.

On the first LD you need to hook up the external coil and then test for spark.

There are ways to test coils but only after you know you have a problem.

There may well be a difference between the condensers but it only matters for a long service life. If the capacitance is off, then one point or the other will pit and transfer metal to its mate. Any good condenser will allow the ignition system to work.

Make sure you are using electrical solder not plumbing solder. Plumbing solder is lead-free so it doesn't contaminate your drinking water. 1/16", 60/40, resin core solder is very easy use but do make sure the working surfaces are scrupulously clean.

You can set the timing easily without sacrificing woodruff keys. You need a piston stop (easy to make with an old plug), a bit stiff wire as a pointer and a measuring tape. Find and mark TDC using the piston stop and pointer (tutorials on the web). Then use the tape measure to measure the circumference of the flywheel. Divide that by 360 and then multiply by 26 to get the distance of the timing point from TDC. Mark it. Set your points so they "just" open at the timing mark.
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Re: Ignition Problems LD's

Postby JLD1 » Fri May 08, 2020 2:51 pm

Hi jbcollier,

Thank you for the information and for getting back to me. It's very useful advice and information.

One other question if you get around to reading this update. On early LD's (pre 54) that have the HT Ignition Wire coming out of the Brown Block / HT Lead Connector, is there any way of checking these? I'm looking at another one of my LD's at the moment that has this setup and wont start. I have not swapped condensor / capacitor yet though? Is it the same, in that I should not expect an electric shock? I have no spark or electric shock when holding the spark plug? I would have thought I would get a spark from this type of set up - or not?

All the best and have a good weekend.
JLD1
 
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Joined: Mon May 14, 2018 10:46 pm

Re: Ignition Problems LD's

Postby jbcollier » Wed May 13, 2020 4:53 pm

Wiring diagram (with self-starter):

https://jbcollier.smugmug.com/Scooter/i-dWQTDpT/A

Some diagnostic info:

https://jbcollier.smugmug.com/Scooter/i-WbLbxkH/A

You can check for grounds and shorts. With the points open the two coils should be isolated.
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Re: Ignition Problems LD's

Postby JLD1 » Sun May 17, 2020 11:30 am

Hi JBCollier

Thanks again for the reply. Fitting an external coil and bypassing the flange mounted bakelite solution for this one solved the problem. I now get a spark / electric shock and it starts first kick, so I can use this while I continue to review the problems and whats wrong with the bakelite solution. Thanks also for the image / page 137 of the Service book.

All the best......
JLD1
 
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