[SilentBob]

Just a guess. Did the bike have a battery to begin with? If not it's probably a half wave rectifier with no regulation. The spikes over 35V could be killing C4 but under the limit of 50V on C5. You'd need a full wave rectifier and regulator.

[Chris Wolfson]

Maybe just leave Speeduino alone for a while and simply fix the generator/ rectifier/ regulator/ batteriy issue of your bike.
You do not install an ignition system on an engine that has no proper 12 V supply. I bet the battery system did not work on the scooter before you startet to convert it to EFI.
Instead of connecting multiple Speeduino´s to a circuit and watch them blow up, normal people FIRST TEST the 12V supply with a multimeter or even scope.
You got to know what AC and DC are, that helps a lot. If you put a diode in a circuit, you still have 1/2 AC which, depending on frequency is not read by the DC position of a voltmeter. If it is digital, it measures about 2 times per second, so you see random values, from the zero crossing up to the peak. Nothing to build any digital electronic on! Maybe you did not know?
So, at last you need a regulator /rectifier that connects to the light coil of your scooter. Then, a working 12V battery to buffer what ever comes out of the regulator. Then you connect the ECU and hope it´s build in voltage conditioner can work with what you throw at them.
I saw your wires. Twisting the end of a cable around something instead of a using a connector made for the task, will blow more Speeduino´s than you can ever build, in no time. Do it once, do it right. Do not try to get along with this ignorant lazy fool´s solutions, NOT EVEN for a TRY!

Ground. If you have no ground, nothing will work. Try to understand the negative side is just as important as any other connection. In fact lazy grounding is the number one cause for ECU systems not working. If there is no perfect ground, the voltage will use any other way to return the electrons. It does not care what it burns down on the way home.

[danizichi]

Maybe just leave Speeduino alone for a while and simply fix the generator/ rectifier/ regulator/ batteriy issue of your bike.
You do not install an ignition system on an engine that has no proper 12 V supply. I bet the battery system did not work on the scooter before you startet to convert it to EFI.
Instead of connecting multiple Speeduino´s to a circuit and watch them blow up, normal people FIRST TEST the 12V supply with a multimeter or even scope.
You got to know what AC and DC are, that helps a lot. If you put a diode in a circuit, you still have 1/2 AC which, depending on frequency is not read by the DC position of a voltmeter. If it is digital, it measures about 2 times per second, so you see random values, from the zero crossing up to the peak. Nothing to build any digital electronic on! Maybe you did not know?
So, at last you need a regulator /rectifier that connects to the light coil of your scooter. Then, a working 12V battery to buffer what ever comes out of the regulator. Then you connect the ECU and hope it´s build in voltage conditioner can work with what you throw at them.
I saw your wires. Twisting the end of a cable around something instead of a using a connector made for the task, will blow more Speeduino´s than you can ever build, in no time. Do it once, do it right. Do not try to get along with this ignorant lazy fool´s solutions, NOT EVEN for a TRY!

Ground. If you have no ground, nothing will work. Try to understand the negative side is just as important as any other connection. In fact lazy grounding is the number one cause for ECU systems not working. If there is no perfect ground, the voltage will use any other way to return the electrons. It does not care what it burns down on the way home.

Thank you so much for the advice!
This night I rebuilded the electricals system, I installed a XL4016 DC-DC convert, now I get a 12 volt DC and 0 volt AC, everything works perfectly. I wired the converter between the stock tensione regulator and speeduino + ignition.
Really thanks for the advices!

Now I need to fix the other speeduino that doesn't sync

[danizichi]

Just a guess. Did the bike have a battery to begin with? If not it's probably a half wave rectifier with no regulation. The spikes over 35V could be killing C4 but under the limit of 50V on C5. You'd need a full wave rectifier and regulator.

I used a tension regulator with battery support. The issue is that I get 13/14 volt DC and 3 Volt AC circa.
Now with a XL4016 DC DC converter I get 0 Volt AC

[Chris Wolfson]

I suppose you use a bridge rectifier between generator coil and DC-DC converter? don´t skip that.

In the end work or work not of any ECU boils down to the crank signal. If it is unstable, anything else is useless.
How do you manage it?
I have not even an idea how a Vespa engine is build, even as I was considered a local 2-stroke specialist 45 years ago

Even as the two stroke engine, in the real world, is virtually dead because of emissions, fitting an ECU to it seems quite interesting.
In (my) theory, tuning the fuel could be quite a challenge, the moment the exhaust gets in resonance.

If you want hints that really help, post pictures, even if you are not too proud of you "Test" constructions. This way someone here maybe can give you ideas what can work and where you chase a dead end.

Today we can do things to such engines, that a few years ago was impossible for DIYS and even manufacturers where not able to do, because of huge investments. Fuel pumps and ECU units have become so small, you can fit them into a lawn mower today.
The improvement on two stroke´s fuel consumption should be impressive.

[danizichi]

I suppose you use a bridge rectifier between generator coil and DC-DC converter? don´t skip that.

In the end work or work not of any ECU boils down to the crank signal. If it is unstable, anything else is useless.
How do you manage it?
I have not even an idea how a Vespa engine is build, even as I was considered a local 2-stroke specialist 45 years ago

Even as the two stroke engine, in the real world, is virtually dead because of emissions, fitting an ECU to it seems quite interesting.
In (my) theory, tuning the fuel could be quite a challenge, the moment the exhaust gets in resonance.

If you want hints that really help, post pictures, even if you are not too proud of you "Test" constructions. This way someone here maybe can give you ideas what can work and where you chase a dead end.

Today we can do things to such engines, that a few years ago was impossible for DIYS and even manufacturers where not able to do, because of huge investments. Fuel pumps and ECU units have become so small, you can fit them into a lawn mower today.
The improvement on two stroke´s fuel consumption should be impressive.

I discovered that the voltage regulator / rectifier was in bad shape. I bought a new one and the problems disappeared!
I have a more question.. I setted spark mode as "single channel" my external rpm gauge read the double of rpm, I need to set spark mode to "sequential"?

Actually I am running ignition only on speeduino, the idea arose from the fact that there are no specific control units for these engines

[Chris Wolfson]

Try playing with tacho settings in the accessories section.

If you got the ignition reliable, fuel should be an easy task. Pump, regulator, TPS and injector. Should be fun and improve running.

[danizichi]

Try playing with tacho settings in the accessories section.

If you got the ignition reliable, fuel should be an easy task. Pump, regulator, TPS and injector. Should be fun and improve running.

My gauge is a kart's instrument, the wire is wrapped around the spark cable

[Chris Wolfson]

I suppose it is for a 4-stroke engine. Chances you do two sparks per revolution are quite low. If you managed to do that, just change it in TS to the right number of cylinders.

If it is 4-stroke, instead of picking up the spark, you sure can modify the rev counter to read the dedicated output of Speeduino. You got to find the input for the spark pick up, identify ground and signal wire and connect to Speeduino. Inside, the instruments circuit will work with a low voltage like 5V.
As always, pictures help a lot.

[danizichi]

I suppose it is for a 4-stroke engine. Chances you do two sparks per revolution are quite low. If you managed to do that, just change it in TS to the right number of cylinders.

If it is 4-stroke, instead of picking up the spark, you sure can modify the rev counter to read the dedicated output of Speeduino. You got to find the input for the spark pick up, identify ground and signal wire and connect to Speeduino. Inside, the instruments circuit will work with a low voltage like 5V.
As always, pictures help a lot.

my actually speeduiino setting is 1 cylinder, 2 stroke, 1 squirt for revoulution, "single channel".
My gauge is designed for 2 stroke mono cylinder engine, so if I read the double of rpm means that apeesuino actually work in wasted spark mode.. and I don't want, because at 12000 rpm one revolution lasts 5ms, barely needed to charge the coil once per revolution