No spark ...but

[Graeme]

Ignominiously arrived home on the back of a tow truck.

No spark on starting but when I take my thumb off the starter, I get a brief spark before it all stops.

Any ideas?  

[Barry]

No spark on starting but when I take my thumb off the starter, I get a brief spark before it all stops.

Any ideas?Smiley

1st clue is it sparks without the starter load so that means given the full 12 volts from the battery it sparks but when cranking the voltage will reduce to maybe 9 volts  and then it doesn't spark.

Could just be the ignition system is marginal and the reduced voltage is enough to stop it working.  I would do a voltage check at the coil to see what you have when cranking. Might just be some bad connections but I suppose it could also be that the electronic ignition module or sensor is faulty.

[Graeme]

Thanks Barry, there's two coils on this bike. Both sides are doi9ng the same; no spark until I stop, then a spark; and a strong one. This happens at the point I remove my thumb from the starter. before that, no spark.

It happened quickly, I arriived at my destination, turned off the bike, an hour & a half later. No start,. I had a push & it ran for maybe three seconds.

[Bob_Roller]

A 'dry' starter, one that needs cleaning and relubrication, can cause your problem .

With a fully charged battery, charged overnight, with the spark plug leads grounded out, check the battery voltage when operating the starter .

Operate the starter for around 45 seconds, to get the 'top charge' off of the battery and see what you get for a voltage reading .

Under 10.2 volts indicates the starter is using more power than it should .

How old is your battery ?

The spark you see at the plugs, is a fairly good indicator that the ignition system is working .

With the plugs removed from the cylinder head and grounded to the cooling fins with the ignition leads still attached to them, turn the key to the 'ON' position, when you do, the plugs should fire, this indicates the ignition system is still working .

These bikes have what is called the 'wasted spark' ignition system, both spark plugs fire at the same time, so if both plugs do the same thing, like I said most likely not an ignition system issue .

This test only works on bikes with the OEM electronic ignition system, contact breaker type ignition equipped bikes won't test this way .

[wilcom]

Are there two different paths for battery to the coils, one for starting and one for running? I looked at the print but it is too small for me to see anymore. If it was a automobile(not a late model electronic POS)your problem  would be an open coil resister 99% of the time

Joe

Riverside, ca

[Bob_Roller]

There's only one electrical circuit for the ignition system .

[Barry]

Are there two different paths for battery to the coils, one for starting and one for running? I looked at the print but it is too small for me to see anymore. If it was a automobile(not a late model electronic POS)your problemwould be an open coil resister 99% of the time

I believe you are thinking of a ballast resistor which is or was commonly used in car ignition systems. It's a very good idea which makes up for the reduced system voltage while cranking but I've never known it applied to bikes and definitely not on airheads.



Graeme

Sounds like you have two 6 volt coils in series which is fine. You should still measure 12 volts or a little more between terminal 15 of the rear coil and earth which will then fall to 10 or below while cranking.  BTW Bob's suggestion of a 45 sec crank will certainly give the system a stiff test but I think Bob means with the plugs removed and grounded to reduce the engine compression load on the starter.  I would never do that with the plugs in. The old adage with wet cell batteries at least is never crank for more than 10 secs at a time with rest periods in between or it will overheat the battery and shorten it's life.

[Graeme]

Hi All

So, today I entered the garage armed with my voltmeter ready to do battle.

(Last night I connected the new battery up to the Battery Saver after I'd finished. The battery was new & purchased that day. All the activity described was carried out with that battery)

I Turned on the ignition with the plugs lying on the fins & heaps of spark ensured.

Replaced plugs, turned on the fuel, waited for a minute for the fuel to get through, choke, turned on ignition, pressed starter button & went almost on the first go.

My suspicion then is on the alternator. I couldn't run that today, The (other) Gorgeous One here is crook so I'll check that on the weekend.

Procedure is to rev to 4000 & check that voltage at the battery is above 14.4?

I'm also suspicious of the switch although I don't know how that could effect starting it's just that at times it doesn't work; I have already purchased from Motobins new handlebar switches for both sides.

Thanks again; I'll report back after I've checked voltage, don't let that put anyone off offering anything further though.  

Tah!

[Barry]

rocedure is to rev to 4000 & check that voltage at the battery is above 14.4?
 

Regulators are nominally 14 volts so 14.4 is at the high end of what you expect to read. In fact it's the maximum safe voltage for a wet cell battery and any higher would indicate a problem with the regulator. Anywhere between 13.8 and 14.2 is within spec. 14.2 - 14.4 is also OK where typical use is mainly short journeys or commuting. The higher voltages can be OK for the AGM type of battery regardless of typical use.

[Bob_Roller]

When you say the starter doesn't work, when you press the start button the starter doesn't rotate, or the starter works, but the engine doesn't fire and run ?

When you can get the time, you may want to check the eclectrical connections for security and corrosion, don't know if residing in Sydney, if you have a problem with corrosion, due to living in a salt water coastal area or not .

Living in a desert for the last 19 years, I have kind of forgotten about corrosion issues .

[Graeme]

Hi Bob.

Starter works, but initially no spark. New battery, charged overnight, plenty of spark & bike starts.

I'm going to check alternator output on the weekend.

And yes, connections were crap; and the ocean's just over the hill (bit like myself   )I went through them about six months ago fixing where I could. I'm trying to get ahead problems before they fail; I am suspecting that the starter motor will be next so after the alternator I'll be doing that. After I got the top ends reco'd, I'm pretty confident about it mechanically now.

[Graeme]

Checked voltage; 13.87. Again, started straight away. Battery fully charged.

[wirewrkr]

13.87 is ideal.

[Graeme]

Then this abhorent behaviour is a mystery then.  [smiley=dankk2.gif]

[Bob_Roller]

About the only thing I can see, looking at a wiring diagram, is to check the fuses for security, the OEM fuse installation, not a great set up .

Loose connections of the fuses in their holders /corrosion, due cause a few electrical issues with these bikes .