No spark - No go

[shambeko]

Out for a run today when the bike suddenly cut out and would not start again, no spark on front plug couldn't get at the rear. Got home eventually with a bit of help from AA and my brother. Had a quck check and there is no spark at either plug. Can anyone give me some pointers of where to start looking tomorrow? It was running fine up till this point.
Thanks
Si

[3potjohn]

Have a look through the checks listed on this site-it may be a bad contact in the circuit or poor earth. I should make double sure any fuses are making good contact.I had a wire rubbed through from the generator,where the leads were held by a clip alongside the generator, but I caught it in time.

[shambeko]

Tried all the checks I could from the site, and a few ideas from Stewert at NLM. Still no sparks. It's going to have to have a trip to NLM when I get time.
Si

[atreyu]

Am I right thinking its a self generating system? If so theres only a couple of parts....Have you tried another coil? If good Id look at the ignition pick-up/back plate? On our racing Greeves we double earth both the coil and pickup plate just to be sure.

[shambeko]

Atreyu, I dont have another coil(transducer) to try. I would think it unlikely they would both pack up together. The stator gives a reading of 300 ohms so looks OK. Which leaves the pickup. Not sure how to check it. I have only visually checked it to see if it turns on kicking.
Si

[EVguru]

The ignition is indeed self generating and has nothing whatsoever to do with the fuses or battery (except in one special case that I'll come to later).

The green wire from the alternator is the high voltage for the ignition. The green wire from the ignition switch connects this to ground to stop the engine, so diss-connect this wire to eliminate it. Do the same for the kill switch wire if your bike has one (electric start models).

You can use an ohm meter to check the pickup. you hould have similar resistance from each trigger wire to ground. Later pickups have a built in diode, so the readings should be very different if you swap the meter leads over. It's not uncommon to have a broken external wire on the pickup. They harden and crack, but can be replaced. Check that you've got a connection between the engine and frame.

A faulty ignition switch, or a stray wire in the fuse panel could result in battery voltage being applied to the transducers via the green wire. This will burn out both transducers and Morini introduced an in-line diode to protect them on later models.

The 'discharger' mentioned in the manual for checking the alternator coil is a 'gas discharge tube' and is usually used to protect circuits against voltage surges. Whilst still available, most these days have ceramic bodies rather than glass, so you can't see them working. Using a multimeter on AC volts should give a reading in the tens of volts whilst kicking over.

[shambeko]

Thanks for the info Paul.
Disconnected the green wires from kill switch and ignition. Still no spark. Meter connected to the pickup red wires gave a reading of ~600ohms with leads connected one way nothing the other. Green wire from alternator gave a reading of about 4v kicked over. Not in the teens as suggested! However when tested for resistence the reading is about 300.

Si

[shambeko]

Finally got the bike sorted thanks to Alex and Stewert at NLM. It looks as if a problem with the ignition switch fried the whole ignition system, stator, pickup and transducers. There should have been a diode fitted to stop this but there wasn't one on my bike so Alex fitted one to prevent it happening again. Also the pickup looked as if was breaking up!. So they had to fit a new rewound stator, 2 transducers and one of their own design pickups.
Luckily for me the bike was still under NLM's 3 month warranty so it only cost me time and petrol money. Otherwise the bill would have been £520.
Thanks again Alex and Stewert for fantastic customer service from NLM.

[Brett]

Hi Guys,

Interesting comments, I have a 74 Sport, and it had the Lucas ignition system fitted, I purchased the NLM pickup and transducer and CDI from them and had no joy in getting a start, I sent them back to NLM and my alternator and they rewound the stator and tested them all with a good result. I re-fitted them to the bike but no spark, I dsconnected the ignition wiring and tried again but no spark, I re-fitted the ignition and suddenly I had a spark in the front cylinder only, then it disappeared, I re checked the rotor in the pickup and ensured the gaps were good, I disconnected the tacho but no joy, I then ran a new wire from the alternator to the transducers but no joy, I tested the earth wire but it was good.......I then removed the NLM system and refitted the Lucas system and first kick she started.

So I am struggling for ideas why I can't get spark....I have tested all of the wiring and earths, and spoke to Stewart at NLM numerous times but even he has run out of ideas.

It has to be something simple, I don't have one here in Australia nearby who can help...so any ideas would be welcome.

Thanks

Brett