Ignition advance/retard

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Ignition advance/retard

Postby Bison » 24 Sep 2017 19:35

Hi Folks,
Been working on the other Morini, 1979 3 1/2 Sport, red pickup, blue transducers. Going great but...
Checked the timing, spot on, wait a minute, how come it's only about 6mm behind the ANT mark at tickover,?. Change the pickup for my spare red one, slightly better but the same really, about maybe 8mm retarded from the ANT (full advance)mark at tickover (1200 rpm or less), when revved goes to the ANT mark, place a diode in line at each transducer, lo and behold, retarding I guess to maybe 12 to 15 degrees advance at tickover, that's around 25 to 28mm from the ANT mark at tickover (toward the TDC mark). I wonder if the diodes in both the red pickups have gone?. My spare one is from my orange bike, which I had ignition advance problems too.
As I have a strobe from way back in the last century, without any advance feature, I wondered if what I have just described sounds like I've got it right?, I doubt it should be ticking over at aprox 28 degrees advanced? (guesstimate). It was starting first kick, hot or cold, not kicking back, but was slightly flat mid range, and when giving it A tutto gas, it would eventually start popping and banging until I laid off the throttle, then run fine, running too hot because it's not retarding enough after revving?.
I suppose riding it would tell a lot, but I just saw an Ark floating down the middle of road with some old geezer with a beard at the helm!
Any constructive comments gratefully received.
PS
Further to this, I said resistor instead of diode, senior moment. And when I max the screen on Sorens video it looks like at 1200 rpm it should be around 21 or 22 degrees advance. The riding of the bike should tell.
Thanks
Alan.
Last edited by Bison on 24 Sep 2017 21:32, edited 3 times in total.
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Re: Ignition advance/retard

Postby 72degrees » 24 Sep 2017 19:38

"Blue transducers". Are these 'Vespa' copies from India?
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Re: Ignition advance/retard

Postby Bison » 24 Sep 2017 19:45

The same but the real thing, made in Italy. The ones Soren talks about.
Alan.
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Re: Ignition advance/retard

Postby 72degrees » 25 Sep 2017 07:03

I see he says they are the same advance curve but it makes me wonder what a substitution with a 'known good' OEM black transducer with green sticker would reveal. Then TBF, he says he can't tell any difference when riding if using 500 red sticker transducers. As long as it's strobing correct at 6000 I wouldn't worry too much as long as it starts and runs OK.
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Re: Ignition advance/retard

Postby Bison » 25 Sep 2017 07:59

I've been told by a friend this morning that NLM said some of the blue transducers do not have a broad enough advance curve, this would tie in with what I'm seeing, and it could be that the fitting of the diodes broaden said curve?, cos that's what seems to be happening. I'll try to get out on the bike tonight and I'll report back.
Alan.
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Re: Ignition advance/retard

Postby harrymuffin » 25 Sep 2017 18:34

Do you really think Mike Hailwood or anyone else bothered with the manual advance and retard on the magnetos of their Manx Nortons once the engine had started, whether hanging on for grim death down Bray Hill or scratching round Ramsey hairpin and then the Gooseneck? Did the BSA/Triumph triples have electronic sophisticated ignition like the Morini? Velocities certainly had advance and retard mechanisms on the road bikes, but they were usually discarded and an alloy fixed timing gear substituted, you just did not let the engine labour at low revs. The whole point of the Heron head was to increase the compression ratio without causing detonation and if any owner can tell the difference without side by side references such as a dynamometer, they are just imagining things, they cannot possibly hear detonation with a full face skid lid, the engine and wind noise, I think they call it a placebo effect in doctoring.
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Re: Ignition advance/retard

Postby Bison » 25 Sep 2017 19:08

Hi,
Well, I guess the answer to that is why did the factory bother in the first place?,
I agree in principal though, about points ignition, I only retard my 45" when I'm labouring it, the rest of the time I leave it alone.
Points systems have a completely different set up, because of the mechanical nature and delays the tickover advance was much lower, if you look at the advance curve of say a Guzzi V35 it looks like a wave, gradual increase then level off, look at the Morini, very steep then levels off. My Jota is a pig in town, primarily because when it gets to, roughly from memory, around 3500 to 4K rpm, it shoots straight to maximum advance from tickover advance, it's either on or off, like a light switch!. No curve, just straight to max advance.
The other thing that worries me are the stories of holed pistons, I would rather be "to be sure to be sure", before I take it to Spain next week.
I would rather be wrong on the forum than wrong on the road.
Thanks
Alan.
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