Ignition Coil Voltage

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dalorian
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Ignition Coil Voltage

Post by dalorian »

I have a 500 with the red pickups and the red dot on black ignition boxes, I get about 30 volts AC coming out of the green wire from the ignition coil while cranking with electric start but absolutely no fire to the plugs . I don't know if the 30 volts cranking with the electric start is adequate for the ignition to fire the plugs ? If anyone has an idea , I would certainly appreciate it.
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72degrees
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Re: Ignition Coil Voltage

Post by 72degrees »

dalorian wrote:I have a 500 with the red pickups and the red dot on black ignition boxes, I get about 30 volts AC coming out of the green wire from the ignition coil while cranking with electric start but absolutely no fire to the plugs . I don't know if the 30 volts cranking with the electric start is adequate for the ignition to fire the plugs ? If anyone has an idea , I would certainly appreciate it.
Sounds a rather on the low side. At least 50 is more like it in my experience just kick starting. What resistance is the ignition winding showing (between green stator wire and earth)?
dalorian
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Re: Ignition Coil Voltage

Post by dalorian »

I get about 212 ohms to ground on the green wire disconnected from the box. Concerning the other terminals on the ignition boxes , when green is disconnected and I put an ohm meter on the terminal where the green wire connects I get 1.83 meg ohms one way only on one box and 1.72 meg ohms on the other box with meter leads one way only . When the meter leads are reversed they measure zero ohms on highest scale which tells me they are pretty consistent on this terminal . On the terminal where the red terminal goes I get 289 ohms and 307 ohms both ways on diode check. Now on the white wire terminal with white wire removed as all the rest wires removed all but the blue ground wire , I get zero ohms to ground , dead short to ground. The plug wires measure about 6.1 K ohms on one and 6.55 K ohms on the other one to ground from the spark plug wire to ground . Now the C.GIRI terminal which measures 33K ohms on one and 34K ohms on the other only has a wire on the left hand box only and no wire on the right hand box for some reason . I don't know if this is normal or not but I don't see a wire that goes to it anywhere. All the measurements are quite consistent with each other and I cannot see any obvious problem with either box or the pick ups as far as ohm meter readings. If anyone has one of the old boxes and pick ups , maybe we could compare notes and learn something on these . I thank you in advance.
dalorian
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Re: Ignition Coil Voltage

Post by dalorian »

I forgot to post the measurements of the red pickups , they are 800 ohms on diode check for one and 811 on the other one just one way only which indicates a diode in each pickup . Zero ohms on each one when meter leads are reversed. Very consistent and close enough it seems.
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Ming
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Re: Ignition Coil Voltage

Post by Ming »

Your ignition coil resistance 'might' be a little low - though resistance is not the best way to be certain, just the easiest to measure.
There is a good explanation of the Morini ignition system on the Dutch Morini Club site (http://www.motomoriniclub.nl/tech.html# ... n%20system) as well as Paul Compton's you tube videos.
Be careful when measuring resistances on the transducers - they are sensitive to DC.
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72degrees
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Re: Ignition Coil Voltage

Post by 72degrees »

As Ming says, the winding resistance is possibly a bit below par, but they will often still spark OK at that if everything else is OK. I've only ever been able to diagnose transducer or pickup problems by substitution test. The other obvious thing to check is that the ignition switch wiring isn't shorting out before the switch. Try hooking the green wire up directly to a transducer with the ignition switch feed disconnected.
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Re: Ignition Coil Voltage

Post by EVguru »

First of all, are you sure you're not getting a spark?

That may sound stupid, but the CDI spark is quite pale and thin and is often difficult to see except in shaddow. NLM tell tales of customers who insist that they're not getting a spark when there is one and the only way to convince them is to have them hold the end of the plug lead and then watch the dancing and swearing.

As I recall, I get about 90VAC at idle on my bike, but we were only getting about 20VAC from the ex NLM racer at kickstart speed (it's a pig to kick over) with a rewound stator. With non folding pegs, you can't usually use a kickstart, but we took the peg off temporarily. It fired up readily on the rollers and was bumping fine later in the day. A weak rotor will reduce the voltage produced.

I had to do a stator swap at the trackday to get someone home. They'd done a number of track sessions and then later had no spark. The failed stator was down to 140 ohm, which indicates quite a few shorted turns. The loan stator was around 215 ohm and worked fine. Normal resistance for the most common type of coil is 220 ohm, NOT 300, although I have come across factory 300 ohm coils.

A secondary factor is that the pickup output voltage is speed dependent, so even if you're getting enough output from the alternator, you might not be getting enough trigger voltage from the pickup if the engine isn't turning over fast enough. I've seen bikes that simply would not start on the starter motor, but would kickstart OK.

That's why I came up with my bench tests for basic functionality.

You can't hurt the ignition boxes with a multimeter.
Paul Compton
http://www.morini-mania.co.uk
http://www.youtube.com/user/EVguru
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Ming
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Re: Ignition Coil Voltage

Post by Ming »

EVguru wrote:...You can't hurt the ignition boxes with a multimeter.
That's good to know.
dalorian
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Re: Ignition Coil Voltage

Post by dalorian »

I was wondering if you have a way to test the boxes with an ohm meter did any of my figures above make any since at all ? do they represent a functioning ignition box ? I checked every terminal trying to get an idea . thanks
dalorian
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Re: Ignition Coil Voltage

Post by dalorian »

Okay , you asked me if I was sure that there was no fire so I disconnected the green wire on the ignition switch and then I cranked it with no plugs in the head and still no spark . Then I grabbed the plugs and grounded myself to the head and I could not feel anything in my hand , not even a tingle. This truly has me stumped.
dalorian
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Re: Ignition Coil Voltage

Post by dalorian »

One more thing that I found when I removed the red pick up and the magnet just now . It appears that the magnet is rubbing on the top pick up , not bad but you can tell where there is some contact. The bottom seems to be clearing but the top is definitely rubbing . Also , how do you tell if someone might have took this off and replaced it 90 degrees off ? I guess you have to take off the cover and check for the timing mark ? Or maybe an easier way ?
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Ming
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Re: Ignition Coil Voltage

Post by Ming »

When you disconnected at the ign switch, did you still have the green wire (from the stator) connected to the transducers?
Even if the pickup is displaced, you should still get a spark - just not at the right point to fire the fuel mixture.
If you do have a rub on the pickup, it may be enough to damage it. Have you checked Paul and Soren's you tube videos on the ignition system? Far more info than I can give!
https://www.youtube.com/results?search_ ... i+ignition
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72degrees
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Re: Ignition Coil Voltage

Post by 72degrees »

dalorian wrote:One more thing that I found when I removed the red pick up and the magnet just now . It appears that the magnet is rubbing on the top pick up , not bad but you can tell where there is some contact. The bottom seems to be clearing but the top is definitely rubbing . Also , how do you tell if someone might have took this off and replaced it 90 degrees off ? I guess you have to take off the cover and check for the timing mark ? Or maybe an easier way ?
The pickup rotor making contact doesn't sound good. Even if the magnet/rotor is 180 degrees out (the only way it really can go back 'wrong' given the flats on the camshaft) you would still have a spark - just not at the right time. It wouldn't start but the spark should be detectable. I had a magnet come loose once (a mistake with washers when converting to a mechanical tacho drive) but that was very obvious when it eventually failed to produce sparks.

Did you disconnect the ignition switch connection as close to the stator as possible? It's a long time since I worked on a 350, not a 250 so I'm not sure of the exact wiring setup. The certain way is to disconnect all the ignition wiring run a wire direct from the green stator connection to just one transducer and check for a spark straight from the HT lead (no cap) with each pickup red connection. If still no spark, try the same with the other transducer. If no spark from either then, the probability is high that the problem is with the pickup.

Time to beg, borrow or steal a known good pickup. I'm so paranoid about them that on really long trips I carry a spare.
dalorian
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Re: Ignition Coil Voltage

Post by dalorian »

When I checked this, I disconnected the green wire from the ignition switch but it did not make much difference . I also disconnected the green wire from the boxes when checking the voltage output while cranking. The magnet on the pickups seems strong and both pickups measure the same impedance with a diode in them. about to pull my hair out.
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Re: Ignition Coil Voltage

Post by norbert »

Did you have in mind the kill-switch? There is also a green cable that should be disconected to be sure that the problem is not there.
A few weeks ago I changed stator and boxes and was desperately thinking of changig the pickup as well, beeing sure that all those components were all right, till I noticed that the kill-switch was on (at this bike it is integrated in the lihgt switch and it didn´t come up to my mind during a cuple of hours :roll: :lol: )
I´ve had ignicion coills with less than 200 ohms without starting problems. My experience is that real kickstarting problems begin with less than 180 ohms if the rest is ok and the flywheel is one of the last generation.
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