Varitronic/Vespatronic timing

[KTy]

Did anyone actually measured the ignition timing after fitting a vari/vespatronic on a Lami/PX/Smallframe ??

Basically my question is; Once fitted according to insctructions, is the ignition timing (top curve) the following for all scooters ?! Cannot be true...

http://www.lambretta.it/special_parts/vespatronic01.pdf

Bearbeitet 11. Mai 2009 von KTy

[T5Rainer]

I´ve just measured a Vespatronic at a 133 ccm smallframe.

Retards the ignition about 8° between highest (25° at app. 3500 U/Min) and lowest (17° at app. 8000 U/Min) figure.

Exactly, what the top curve says.

Edit: Why do You doubt?

Bearbeitet 11. Mai 2009 von T5Rainer

[KTy]

Hi T5Rainer,

thanks for the info;

But I can see that your figures are not exactly the same as the curve ! At 3500rpm, curve says 23°, and 15° at 8000rpm; That's 2° difference compared to your measurements !

I have some doubt because I do not really expect, for instance, a 225cc longstroke largeframe engine and a 125cc M1L Quattrini to have the same ignition timings... I think the varitronic manual tells you to set the ignition this way or this way and it actually shifts the curve according to the engine type.

I agree that with +/-5° every curve should be the same, basically, same shape; but in your case 2° difference at 8000rpm is really a lot !

Thanks again, your inputs are useful !

Bearbeitet 11. Mai 2009 von KTy

[T5Rainer]

But I can see that your figures are not exactly the same as the curve ! At 3500rpm, curve says 23°, and 15° at 8000rpm; That's 2° difference compared to your measurements !

The curve with 23° to 15° is just an example.

You can give it every figure You want by turning the plate. Only the the retard of 8° ist fix.

The user of the smallframe wished 17° at high rev.

[Brosi]

OK, I get it.

Of course the curve does not fit automatically.

You have to ajust the position of the curve, just as with the normal Ignition.

Meaning: You make your markings at OT and, let´s say, 23° and turn the base plate and check the ignition at the plateau (maximum angle b.t.d.c.).

So if Rainer would turn his igniton exactly 2° clockwise he would exactly get the ignition curve shown in the manual.

Bearbeitet 11. Mai 2009 von Brosi

[KTy]

Guys

I understand that !

I was just wondering what is the "exact real" timing advance curve when you mount the stator ACCORDING to the "official" instructions.

I am working on this

Sorry for making things confusing !

Bearbeitet 11. Mai 2009 von KTy

[Lacknase]

The "real" timing advance varies. (As long as one would try to measure timings with a stroboscope and rpm meter, that is. And I think most people here do.) Just because the air/gas mixture influences the "real" advance as identified with/deduced from ignition (impulse via induction lead attached to the plug wire).