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Ignition set up

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

Ignition set up

Postby mm man » Sun Oct 06, 2019 9:47 am

Hi
What the best ignition set up to have on a 54 D on a standard crank for reliability and starting ?
Or do you have to go down the li route ? Is it worth it ?
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Re: Ignition set up

Postby jbcollier » Sun Oct 06, 2019 1:52 pm

I'm happily using this:

http://www.lambretta.co.uk/shop/advance ... c&x=9&y=11

Works very well.
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Re: Ignition set up

Postby mm man » Sun Oct 06, 2019 4:40 pm

jbcollier wrote:I'm happily using this:

http://www.lambretta.co.uk/shop/advance ... c&x=9&y=11

Works very well.


Thanks for your reply
I’ve seen theses do they retard enough for easy starting on a D?
Do you know if these are a standard kit ie the same as all the other Lambretta Varitronic set ups but just have a smaller flywheel taper to match the D crank or are the built in advance and retard curves different for each model ? Or am I talking nonsense. ;)
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Re: Ignition set up

Postby jbcollier » Mon Oct 07, 2019 2:47 pm

The variatronics all use the same basic components. They have:

- different flywheel centres to suit different crank tapers

- different fans (the D rotates in the opposite direction to an Li/TV/DL/GP)

- different stator mounting plates to suit

The ignition starts out advanced and then retards slowly as the revs build.

The stock D/LD system is crazy. Retarded timing while cranking is not needed. I run a long stroke crank and a squish head and so have far higher compression than a stock engine. Never, ever has the engine kicked back.
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Re: Ignition set up

Postby Steve J » Wed Oct 09, 2019 4:58 pm

There's your answer, it's the squish head that helps prevent detonation! My experience with the standard hemispherical head (without any squish band) on a 150 engine was that it would occasionally kick back, even with a fully working advance mechanism. Mind you, I probably didn't help matters by using a skimmed head..... :(

I don't believe the Varitronic ignitions provide any substantial ignition retardation for starting, and only start to retard the ignition at engine speeds way above the normal operating band of a D/LD engine. On the other hand, the original Marelli or Filso ignitions would give a timing of around 8 degrees BTDC for starting, advancing to 26 degrees BTDC by the time the engine reached around 1,800 rpm, and remaining at that figure for all higher engine speeds. Although it provides breakerless ignition for D/LD engines, I fail to see why the Varitronic's ability to retard the ignition to prevent detonation above about 6,000 rpm is of benefit on an engine which maxes out below 5,000 rpm!
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Re: Ignition set up

Postby jbcollier » Thu Oct 10, 2019 12:55 pm

The higher rpm retard is useful for me as I also have an expansion pipe so mine revs higher as well. On the flat I get a little over 100 kph.
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Re: Ignition set up

Postby Steve J » Fri Oct 11, 2019 11:08 am

jbcollier wrote:On the flat I get a little over 100 kph.


Brave man! I once got an indicated 68mph on my LD down a long steep hill... :shock: Scared me to death, never tried it again!
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Re: Ignition set up

Postby Fast n Furious » Fri Oct 11, 2019 2:33 pm

jbcollier wrote:The stock D/LD system is crazy. Retarded timing while cranking is not needed. I run a long stroke crank and a squish head and so have far higher compression than a stock engine. Never, ever has the engine kicked back.

By retarding it upon start up, it makes it easier to start for the inexperienced and its more an insurance policy to ensure it doesn't kick back which would have been seen as quite damming back in the day considering the markets that they were originally intended for. Lots of other old motorcycles employ the same reasoning.
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