Varitronic timing setting

[Adam_Winstone]

There seems to be a little confusion here as to what the requirements are for which engine and with which version of the Varitronic. I've had a quick look at the link to recent fitting instructions but they cover a huge range of motors, with very different compression ratios, operating RPM ranges, pipe characteristics, porting specs and therefore need some very different timing settings (starting, mid range and full RPM). Much of the setting information is great for a kitted high BHP/high revving motor, which is confusing the requirement for a standard Cento motor.

I for one wouldn't want to guess what setting I should be running at (well, I would... but I'd also take responsibility for potentially getting it wrong and blowing it up!), rather, I'd go back to the supplier and ask them for their recommendation. Centos are quite different to the SI - SIII motors that many of us have experience of setting up variable ignitions, especially kitted motors that have massively different timing requirements, so I'd not want to start guessing at your expense. I can't even remember what timing I ended up with on the Cento, J125, and my own Starstream 125 converted Vega but I do recall that they don't need to be retarded as far as even a standard SIII running on today's fuel, which will be related to the low port specs and fairly low compression and low revving pipe.

My advice would be to email Cambridge Lambretta, Tino or a.n.other supplier and see what first-hand experience they have and/or for their recommendation.

Nelson is quite right that I've made previous comments about people getting advance/retard settings wrong (even getting the starting point or end point right but having the wrong ignition curve profile for your a specific motor), which can leave you running too advanced and overheating (seizure or piston holing) or too retarded and the motor losing most of the power that it would otherwise be making. Too many people get their setting wrong and then blame it on the ignition kit, whereas they should be concentrating on getting the settings right.

Best of luck.

Adam

PS - I know that I said I'd not be guessing your timing requirements but I will give you something to consider...

The standard ignition requirement for a J100 was (pre-unleaded, pre-ethanol, when pump petrol burned cooler) 24 degrees btdc, in the same way that most SIIIs were 23 degrees btdc and higher revving GPs were running 21 as standard. Most people are now running lower spec SIIIs on 19 degrees btdc, higher revving standard'ish motors at 17 degrees btdc and kits often at 16 or less! Following this logic and basic reduction in advance, to keep cool, you may also want to be looking for your 24 (original 60s timing) to 19 degrees at maximum revs. To improve low rev power and gain a performance improvement from your investment in this ignition kit, the starting point (fast tickover) may well be back at the original 60's firing point of 24... or more advanced, which will give more power when pulling away from a standing start and assist massively when carrying a passenger. Remember that you must get the timing too advanced and it will overheat and cause issue.... but too retarded (closer to TDC) and the motor will make little/no power

In order to get this right YOU MUST be able to strobe your ignition timing to see what the range of firing point is, from tickover to maximum revs (you'll do this on the stand and see the firing point swing over the range, retarding as revs rise). There should be no 'guessing' when it comes to setting ANY electronic ignition, especially not an auto advance/retard ignition.

[Nerdy Norm]

Adam, many thanks for your detailed response.

I emailed Tino a few days ago, but no reply has been received. Does anyone know if he understands English? I also emailed Scooter Centre Cologne who sold me the kit, but again, no answer as yet.

I notice that the instructions supplied with the kit are generic for pretty much all models, from a Lui to a GP. Going by their advice of 25 degrees at 2000 - 4000rpm for a standard motor, that would mean that a Cento would be at 22 degrees when developing its maximum power (all 4.7hp of it!) at 5300rpm.

To arrive at your advised (without prejudice) peak power figure of 19 degrees, and assuming that the curve on the graph is correct, it would mean a fast idle setting of 22 degrees. So 22 degrees at between 2000 and 4000rpm, closing to 19 degrees at the peak-power revs of 5300rpm.

Does this sound reasonable? If so, it will require quite a lot of metal removing from the slots.

Thanks again for your insight!

[Adam_Winstone]

Tino does speak pretty good English but he is a very busy guy. If your message was a long one then it might be best running it through Google translator and resending it, which might make it easier for him to have a quick read, rather than needing to translate it himself. He's a very nice guy and a Lambretta enthusiast through and through.

Personally, I'd not trust any graph or profile (especially as I understand that the early ignition curve profile was quite different to the later ones). I would not go by any estimation of where it will start and where it will end up at max revs, rather, I would mark the edge of flywheel or mag housing to accurately show a range of firing points from something like 15 degrees to 30 degrees, then fit it, strobe it and watch where it goes from and to, then adjust accordingly by rotating the stator (I have had to elongate stator slots on other bolt-on advance/retard options).

As the standard Varitronic, for SI-SIII, uses a different base plate to Luna and J models, I would not be surprised to learn that the curve profile or recommended settings differ also, hence me stressing the point that I'd speak to those that might have first-hand experience (before you start modifying).

I am aware that the Varitronic curve also used to start quite retarded (for ease of kick starting), then advance a little (to give low rev power), then retard through the rev range (to keep it cool/safe at higher revs). As such, I'd actually want to see what this means in reality for your motor. As such, your motor might not simply go from 22 to 19 but start at 22, then go the other way, then work its way to 19... none of which you would be likely to predict from the info available to you currently.

I'd be very surprised to learn that your Varitronic only gives you 3 degrees of retard (another reason for me suggesting that you strobe it to see the range).

Hopefully, others on this forum (or others) might have first-hand experience and be able to offer you better instruction than I can. It might be worth sending emails to others that specialise in J and Luna models to see what they might be able to offer in the way of advice, although you may find that many are fitting this ignition when fitting it with the J and Luna kits that are now available.

Stick with it and we'll get you sorted out

Adam

[Nerdy Norm]

Thanks again Adam.

I've emailed Tino again with a very short note, also translated into Italian with Google, so hopefully it'll make sense.

I believe that the system retards by up to 8 degrees, however the Cento makes its maximum power at 5300rpm, which (according to the graph, which is generic for all models) gives a maximum of 3 degrees. It would need to rev all the way past 8000rpm to achieve the full 8 degrees of retard.

It does make me wonder why Tino would go to the trouble of supplying generic instructions which it seems are completely incorrect

Fingers crossed that I hear back from Tino and/or Scooter Centre.

[Nerdy Norm]

Just heard back from Scooter Centre Cologne:
"You should put the Ignition on 25° to come to 17° at 6000 RPM."

So that's where I already was - let's give it a couple of days and see if Tino comes up with the same advice ...

[Adam_Winstone]

^... sounds perfectly good to me

[wack 63]

Looking at the graph you will see fast idle is set at 23 degrees and stays there until 4000 revs then by 6000 its retarded to 18*, so what the Germans have told you is wrong. Personally I would aim for 19-20 degrees around peak power after all it's a standard motor that was originally set as a compromise at 23-24 deg BTDC.

[Nerdy Norm]

Aaaaaagh! I'm going round in circles

The instructions on the packaging (the same for all Lambretta models) say to set it at 25 or 26 degrees at 2000rpm for a standard engine.
The graph on the same instructions shows 23 degrees at 2000rpm.
Scooter Center says 25 degrees.
Others on this thread say either 20, 21, 22 or 24.

I wish Tino would break his silence

[Adam_Winstone]

Two things:

1. I think that you're worrying too much about finding a definitive instruction as to what you should be setting your specific motor to. Unfortunately, no 2 motors are the same and I know of similar motor where one is running low compression at 21 and the other high compression at 16 (both static timing)! Regardless of what information you find, it should only ever be considered as a starting point... for you to test and verify, or adjust according to your findings (plug colour, plug tests, sound of pinking, engine temperature, etc.). As such, even if you do find an instruction in print, you still need to keep an eye and ear open when assessing it. NB: You are also quite likely to find that fitting a variable ignition can require you to reassess your jetting too... again, subject to testing.

2. Many people set their variable ignitions by aiming for a certain firing point that will keep it cool when riding at a constant high speed, rather than worry about what it is starting at for tickover. At lower speeds the motor is more forgiving (wider margin for error) and it is at higher revs/speeds that you are most likely to run into problems if your timing is out. As a result of this, many people will start by strobing to ensure that the motor retards to their max rev RPM target, (e.g. 17 degrees at 6500 RPM) or beyond (cooler running and safer but may lose a little power), then see what that advances back to at tickover or 2000 RPM. By worrying too much about tickover you might be looking at the wrong end of the range, with max revs and mid-range cruising revs being more important.

Remember that too much advance can lead to damage (overheating, piston holing, seizure, etc.), whereas too little advance (= more retard) is likely to result in a loss of power but run cooler/safer. As such, I'd look to start with less advance at tickover, assess, then adjust (rotate stator to fire with more advance) and reassess.

Don't start to regret buying the Varitronic as you would have exactly the same issue if you had kept the standard static ignition and asked what the static timing should be! Unfortunately, changes in fuel burning temps (60s leaded - unleaded - modern ethanol % unleaded) mean that the 24 btdc quoted by Innocenti would no longer apply either. Answers to that question could range anywhere between 24 and 17, with whatever you opted for needing to be assessed anyway.

Indeed, you (yes, YOU!) will influence the timing that your bike needs also. If you use (still thinking in terms of static ignition timing) this bike in town only then the 24 btdc might be fine, however, if you want to ride this on long straight roads to Euro Lambretta then you might want it set to 18 dbtdc to stay cool and reliable. The joy of your new Varitronic is that you should be able to ride around town at 24 AND then ride it on long straight roads at 18 degrees, without getting your hands dirty

Mark up the timing range, make sure that you've done up the flywheel nut tightly (!), then rev the bike to max revs and see what mark the timing retards to. Don't keep it revving for long, just long enough to see what the timing retards to. If your motor starts to retard as revs increase BUT then bogs down, this can be caused by the ignition retarding too far and struggling to burn off the fuel mix... as the revs drop and the timing advances the motor would burn the mix off and run better. Lots of people make the mistake of starting too low and going well past the target max rev timing, which causes the bike to run badly, lose power and lose speed... then blame the ignition

You will need to adjust your timing to suit your engine... any recommended settings are only a starting point.

Good luck.

Adam

[Nerdy Norm]

Thanks again Adam.

I'm starting to lose the will to continue with this, it's way out of my comfort zone. I only bought the Varitronic so that I could get 12 volt lighting and electronic ignition (normal electronic ignition kits are not available for the J-range). The points system was working fine, but I just didn't like the idea of having to adjust the gaps or whatever it is you have to do with them. And I don't have any cigarette papers

On my LI series 3, I fitted a Casa 185 kit and Indian electronic ignition (eventually swapping it for a BGM stator). I set the timing at 19 degrees (as advised by RLC), and it just works. Around town, motorways, whatever - it hasn't missed a beat. I was hoping that the Varitronic would be the same.

Realistically, the Cento is going to spend a lot of its time flat out, since that's what you have to do to keep up with suburban traffic on a scooter that maxes out at forty-odd.

Part of me thinks that I've spent so much time and effort on this, I have to see it through. But the other half is saying just put the points stuff back on and ride the damn thing!

Maybe the best thing is just to park the whole idea until the spring, when maybe my patience will return. Thanks again to everyone for their encouragement.