Varitronic timing setting

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Nerdy Norm
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I've just fitted a Varitronic ignition to replace the original points system on my J100 Cento. A couple of questions for the experts:

1. The flywheel doesn't have any arrow marked on it. Am I right in thinking that I can just make my own mark anywhere, or must it be in a specific place?

2. I've tripled checked my TDC marking on the casing (using a piston stopper), but I can't get the timing anywhere near the recommended setting of 21 degrees BTDC at fast idle. Even at the very ends of the slots, it's firing at around 27 degrees BTDC (using a basic strobe gun). If I cut out the ends of the slots to allow more rotation, I'll only be able to fit 2 of the 3 stator bolts as the third will be blocked by a mag housing nut.

Any ideas chaps?
Lambretta LI125 Series 2, Lambretta LI150 Series 3, Lambretta J100 Cento, LML Star 150 2T
dapper
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Yes, arrow can go anywhere, as its just a reference point as to where the firing point is relative to the rotation of the crank. Sometimes, changing the spark plug gap can assist you in getting the correct firing point BTDC (ie, closer or farther apart)
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Nerdy Norm
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Thanks Dapper. It's a new (genuine) NGK plug. I didn't check the gap, but I never have done before, and didn't have a problem with timing on other scooters - would it really make such a huge difference?

Since the adjustment range of the slots is normally, let's say, something like 18 to 24 degrees, the centre position would be around 21 degrees. The centre position on my setup gives around 30 degrees, so it seems like the whole stator plate is out by around 10 degrees.

I don't really want to start chopping chunks out of my new £300 ignition system, but I'm completely stumped.
Lambretta LI125 Series 2, Lambretta LI150 Series 3, Lambretta J100 Cento, LML Star 150 2T
Chris in Margate
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Pick up fitted wrongly out of position on new stator ?
Nerdy Norm
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Chris, the stator components certainly look identical to photos I've seen, so I don't think so.
Lambretta LI125 Series 2, Lambretta LI150 Series 3, Lambretta J100 Cento, LML Star 150 2T
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wack 63
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Why would you want to set it at 21* at fast idle? Presuming you have always run factory setting with your points system this is where you want to be aiming for at high revs. You've got 8* of retard so if the fast idle is 24* then the timing starts to retard at 4000 rpm so by the time you hit 6k the timing will be around 20* , going lower if the bike revs more. If you are positive regards the TDC marks then the only alternative is to elongate the stator slots and maybe change the stud for a countersunk screw.
Nerdy Norm
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Thanks Wack - I took the 21 degree setting from Cam Lam's instructions:
"At fast idle, set the timing to either 21 degrees if using a standard / big bore / Ancillotti type exhaust, or 19 degrees if using any expansion chamber."
http://www.lambretta.co.uk/downloads/va ... tting.html

The engine is a completely standard (recently rebored) J100 Cento, with standard carb and exhaust. I haven't dared crank up the revs yet since the timing seemed so far out, I didn't want to risk any damage.

As it stands, fitting it at the mid position of the slots (presumably this should be where factory-standard timing would be) gives around 30 degrees. The most I can advance it to without drastic surgery is about 27 degrees.

If you guys think it sounds OK, I'll go with it, but it just seemed a long way away from standard.
Lambretta LI125 Series 2, Lambretta LI150 Series 3, Lambretta J100 Cento, LML Star 150 2T
Nerdy Norm
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Update: I've finally sorted out the timing - it was a combination of my mistake and duff info.

My mistake: despite triple-checking the TDC point, I somehow managed to mess it up :?

Duff info - Cambridge Lambretta say that it should be set at 21 degrees at fast idle. Elsewhere (both on this and other forums, as well as the fairly basic instructions supplied with the kit) it's suggested to set the timing at 25 degrees BTDC at fast idle. This makes sense as the Varitronic stays at around this until 4000rpm at which point it starts advancing by up to 8 degrees, therefore ending up at around 17 degrees at maximum revs.

No road test yet as I still need to sort out the wiring (see another thread), but it starts and runs fine now.
Lambretta LI125 Series 2, Lambretta LI150 Series 3, Lambretta J100 Cento, LML Star 150 2T
nelson pk
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Hold on! Before setting your timing at 25 degrees at idle.....no one has asked what kit you have got or whether the bike is standard etc, etc.

The reason that Cam lam state 21 degrees is safety.....it is not unknown for too advanced timing to make a scoot go pop in the mid range especially if one other setting like jetting or compression is slightly out and then you are running at 20 degrees at 5000 rpm for example for a long while causing excessive heat and problems!

I believe Adam Winstone has mentioned on here that he has also seen similar failures on advance/retard units too.

If you set at 20 or 21 degrees you still get the benefit of slightly advanced timing at lower revs (and this is the key area where these units help) and yes it may retard back to say 14 degrees at full revs but the difference between say 16 degrees at full revs and 14 degrees in power terms is negligible or not worth worrying about on a road scoot.

Its up to you but I would stick to the instructions based on info from their tuners dyno. It is not duff info!
Nerdy Norm
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Thanks Nelson. As mentioned a couple of posts back, the scooter is completely standard, no kit or expansion exhaust.

According to Tino's instructions, standard engines with a maximum speed of 6000rpm should be set to 25 to 26 degrees, whilst tuned engines with high compression and a speed of over 7000rpm should be set at between 19 and 24 degrees. These should be set between 2000 and 4000rpm (i.e. before the retarding starts).
http://www.lambretta.it/foto_gestione/p ... c_2012.pdf

Don't forget that this is a Cento we're talking about, with a maximum speed of around forty-odd. I'm keen to not reduce this if at all possible ;)

So the question is whether I go with the manufacturer's instructions or not?
Lambretta LI125 Series 2, Lambretta LI150 Series 3, Lambretta J100 Cento, LML Star 150 2T
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