Ignition pickup coil output.

[stinkwheel]

I'm fault finding a basic AC ignition system. It's actually one of the really common GY6 chinese ones.

I'm getting a decent AC voltage spike from the CDI power coil, in the 20v range. Coil seems good and I've tried two different ones but the spark is intermittant.

Anyway, I thought I'd best check the pickup is pulsing to the CDI because the trigger is a bit unconventional, it's not rotor mounted but is a custom made trigger that mounts on the crank taper.

I got a cheap, single channel oscilloscope because this is the third time in the last 12 months I've been in need of one.

So I'm getting a pointy 0.4 to 0.85v spike. Explaining the timebase, it's a kick start bike and I get roughly three revolutions per kick with the plug out so those clusters of three do match up with the engine revolutions and the smaller spikes match with the slower rotation.

Does this seem about right?

https://lh3.googleusercontent.com/pw/AP1GczND3KeoJ7zPyXM3Q6t_Y_puYy55oeAQPDk1jT8FmpxUDPYpVLGoDK7jjVIaLR70t4K36lhKIhyL691QZUdQqqDE6ljQlguradMEESLOR7LHIDInyeBBmLDHMITsLWZ6knS1WMEPjGiyovo-L3HhsNzE=w1557-h876-s-no
____________________
“Rule one: Always stick around for one more drink. That's when things happen. That's when you find out everything you want to know.”
I did the 2010 Round Britain Rally on my 350 Bullet. 89 landmarks, 3 months, 9,500 miles.

[Easy-X]

Any way to turn over the motor with a drill to get a more consistent output?
____________________
Royal Enfield Continental GT 535, Husqvarna Vitpilen 401, Yamaha XSR700, Honda Rebel, Yamaha DT175, Suzuki SV650 (loan) Fazer 600, Keeway Superlight 125, 50cc turd scooter

[stinkwheel]

[Easy-X]

Well it doesn't look great given the symptom is intermittent spark but to be absolutely certain one would need to compare to a working system - easier said than done
____________________
Royal Enfield Continental GT 535, Husqvarna Vitpilen 401, Yamaha XSR700, Honda Rebel, Yamaha DT175, Suzuki SV650 (loan) Fazer 600, Keeway Superlight 125, 50cc turd scooter

[A100man]

I'd expect it to be more consistent.
It's possible the sample rate of the scope is not high enough at that timebase and you're not seing a true representation, turn up the timebase so you can only see a couple of pulses and see if they become more even. Maybe try 'single shot' mode.
____________________
Now: A100, GT250A, XJ598, FZ750

Then: Fizz, RS200, KL250, XJ550, Laverda Alpina, XJ600, FZS600

[WD Forte]

I dont know the circuitry so cant say for sure, but would like to see a wee bit more voltage than that as a lot of SCRs need around a minimum voltage of say 1.2V possibly more to trigger.
If they triggered too low they'd be firing at every transient spike.

If its running off the crankshaft, the diameter will be relatively small and the rotational speed past the coil lower than a pulser fixed on the outside of a rotor so have a comparatively lower voltage.

If I had to get pulses off a crank I might consider a Hall effect switch or a chopper over a reluctor type which relies on proximity and speed to produce a decent signal pulse.
Maybe even points as just a signal source unlike its typical use as
a combined signal + power source.

Its quite possible to boost the signal with a basic amp but you'd have to filter out the noise and extraneous pulses so it may not be a s simple as we'd like.
Well done sticking a scope on it, now you can see what's going on
handy fings scopes.
____________________
bikers smell of wee

[WD Forte]

On the old Cx's with AC-CDI
when checking CDI to coil output with a meter set to DC
( yes DC cos it's a pulsed DC)
I'd expect to see an erratic voltage of 150-200 V open circuit
output to the coil when cranking on the starter
It was my crude but effective quick test
and if I saw this I knew the CDI box was OK
If I saw sub 100V it was suspect, sub 50V fooked

Not sure if any of the above applies to the GY6 box but it should be somewhat similar
____________________
bikers smell of wee

[stinkwheel]

Cool, I have stuff to check. It was working before but the charging coils on the stator went thermonuclear, probably due to it constantly dumping because of having zero load on it. I've resigned myself to it probably needing a battery and I replaced the stator coils with a more basic AC/DC setup in a C90 style (yellow, white and earth) but will never use the AC side, so like riding a C90 during the day.

It took out the ignition source coil too (lucky there wasn't a fire really). Stator comes with one fitted and while the pulse coil looks identical, I have suspicions about it maybe being a bit out of kilter either with signal or clearance. I'll get the whole lot up on the lift. It's just hard to reach. I can look at the pulse coil but only with the stator coils removed from the back plate. Now I have a scope, I suppose I can just remove them for a bit and tune in the pulse coil., then worry about the rest of it. I think the old one is actually ok so I can compare that too.

I turned down the timebase as suggested by A100man. Looks like it's pulsing regularly, Perhaps just not a high enough waveform to trigger the spark? Only getting 0.3V. Ovalling out the the holes in the stator plate and dialling in the gap between the trigger and the pickup is probably the first step?

https://lh3.googleusercontent.com/pw/AP1GczO8W5hmTBsO_5_ECxv17KMD-a7UgAV9mJOyhnni4CkRJ2QNk7v6FZQxIGwOKh4pNugfzrk9zfMRdz3QslA6ipdI3nyNAAvPgfOlPm9jUrdtSsQ_3Qs2QHEZDgqwjZeyPJFV2irDwtHXcgVC89SQKPps=w1557-h876-s-no
____________________
“Rule one: Always stick around for one more drink. That's when things happen. That's when you find out everything you want to know.”
I did the 2010 Round Britain Rally on my 350 Bullet. 89 landmarks, 3 months, 9,500 miles.

[Easy-X]

I doubt 0.3V is enough for anything in the CDI given that's the minimum requirement for a Germanium diode to work (Silicon diodes need at least 0.7V)
____________________
Royal Enfield Continental GT 535, Husqvarna Vitpilen 401, Yamaha XSR700, Honda Rebel, Yamaha DT175, Suzuki SV650 (loan) Fazer 600, Keeway Superlight 125, 50cc turd scooter

[WD Forte]

That waveform looks a pretty typical pulse with some ringing
but 300mV aint gonna do shit to use a technical term.
A closer gap and more windings on the pickup may help
or
stuff I mentioned above
or
Devise a cunning plan to mount a pickup on the outside of the rotor
where the higher rotational speed will produce a stronger pulse
or
Stick a magnet or shiny thing on the outside for a Hall or opto pickup
to detect as it whizzes past
____________________
bikers smell of wee

[stinkwheel]

Oh, I think the noise on the signal may be the mains powered electric drill I was using to turn the engine.

It's good I found this anyway, this will almost certainly be why I have intermitant sparking.

I should be able to make it work with this setup. The bike's done over 500 miles without a glitch on the ignition side. It's got to be either a misaligned/mis-gapped sensor or a dodgy sensor.

I just didn't want to have to take all this stuff apart again but I'm going to have to. I effectively just want the pickup coil and bare stator plate and need to keep tinkering until I get a better signal.

Here's the pickup. As you can see, it's pretty tight for space in there, with the stator and rotor fitted, the space is pretty much full. I can't see any way I could mount a trigger on the rotor. Also, the rotor isn't keyed.

https://lh3.googleusercontent.com/pw/AP1GczNUpJ3GqFqYsGeY3GoeVvdh_roKmrZJlgerzs-GniT_XdaexUr5A6K4S3ct6j9agfmQ0dMnLowUb7SRsxyfHN34VBlsR-Aiwi48iW08_yckNBTgKFGykfImojj5LFaTcyD6jvKam3kV3lo1aHjGkdos=w1557-h876-s-no

I'll keep things updated. I'm enjoying playing with my new gadget anyway so that makes the faffery less annoying. It'll also be better when I get Mrs stinkwheels bike off the lift so i can work at eye level instead of grubbing about on the floor.
____________________
“Rule one: Always stick around for one more drink. That's when things happen. That's when you find out everything you want to know.”
I did the 2010 Round Britain Rally on my 350 Bullet. 89 landmarks, 3 months, 9,500 miles.

[WD Forte]

Maybe, but I doubt its the drill motor as its frequency would be much higher and more consistent than your cranking speed waveform.
Your last waveform looks pretty typical to me, noise and all
the only downside is the amplitude of the pulse.
____________________
bikers smell of wee

[A100man]

some/most scope probes are x10 attenuating. It looks like your scope is set to x1. Perhaps worth checking what's written on teh probe or check against the 'Cal.' signal of the scope if it has one.
____________________
Now: A100, GT250A, XJ598, FZ750

Then: Fizz, RS200, KL250, XJ550, Laverda Alpina, XJ600, FZS600

[stinkwheel]

[stinkwheel]

Update on this. I swapped out the pickup coil for the one off the burned out stator. Which is identical in every respect including clearances and coil resistance. It's giving the same profile spike but at 3.2V. It also now makes a spark. So the one I was testing was definately duff.

Goes to show that just because the resistance reading on a pickup coil is good, doesn't mean the coil itself is doing what it's supposed to
____________________
“Rule one: Always stick around for one more drink. That's when things happen. That's when you find out everything you want to know.”
I did the 2010 Round Britain Rally on my 350 Bullet. 89 landmarks, 3 months, 9,500 miles.

[A100man]

Aye.. Resistance alone ain't a great test as I discovered on my failing XJ ignition coils that tested for resistance perfectly.

A new set has absolutely transformed the starting..

(see what I did there..)
____________________
Now: A100, GT250A, XJ598, FZ750

Then: Fizz, RS200, KL250, XJ550, Laverda Alpina, XJ600, FZS600

[lingeringstin...]

[quote="WD Forte"]On the old Cx's with AC-CDI
when checking CDI to coil output with a meter set to DC
( yes DC cos it's a pulsed DC)
I'd expect to see an erratic voltage of 150-200 V open circuit
output to the coil when cranking on the starter
It was my crude but effective quick test
and if I saw this I knew the CDI box was OK
If I saw sub 100V it was suspect, sub 50V fooked

Not sure if any of the above applies to the GY6 box but it should be somewhat similar[/quote]


A CX500 was the only bike I ever had where changing the CDI meant dropping the whole engine out. Whose fucking daft idea was THAT?

[blurredman]

[WD Forte]

[blurredman]