Testing Coils (technical data?)

[Arthur Farrow]

Tested 2 new coils today (Lucas boxed and I suspect made in India) with a swanky NOS AVO I bought at great expense a few months ago

2.0 Ohm LT leads
11.0 K.Ohm HT lead to one LT terminal

Tested 2 coils on bike (date stamped 1977)

2.0 Ohm LT leads
6.0 K.Ohm HT lead to one LT terminal

Via an America website I read that the spec was somewhat lower than this especially on the HT side (1.5 - 2.2 Ohm and 4 K Ohm). I do not take such as gospel unless it comes from God, my mum or the manufacturer. I read that Tri Spark 6V coils have more HT windings and thus I assume more HT grunt and assume these new Lucas jobs are in similar vein.

The new coils certainly seem to bang a nice light blue spark.

Anybody any further data??

[hendred]

Data from original Lucas Motorcycle Service Sheets for 17 M 6 coils:

Primary (LT) resistance 1.7 - 1.9 ohms.  No resistance given for secondary (HT).  Tested on a spark machine.

PVL 6v coil made in Germany to original Lucas 17 M 6 Spec:

Primary resistance 1.7 - 1.9 ohms.  Secondary resistance 6K ohms.

My original Lucas coils were measured for another thread on this topic on this site and were about 1.9 ohms.  Secondary not measured.  Looks like your old Lucas coils are within spec.  Unfortunately testing with an AVO won't necessarily show up a defective  coil which breaks down when generating high voltage.

The resistance of the secondary is determined by the number of turns and the resistance of the wire.  A thin wire has a higher resistance than a thick wire.  Whether the higher secondary resistance coils have a higher energy spark will depend on the overall design of the coil.  

[Arthur Farrow]

Great and good to have proper data. I agree with what you say. The new coils are delicately producing a "different spark" in time will see if it helped erratic starting.