no spark at plug

[roadster]

The coil is essentially a transformer where the input is high current - low voltage and the output is low current - high voltage. The high current on the twelve volt side should be measurable by briefly applying 12 volts and if massive current indicates a dead short its faulty, if there is no current its faulty. Measuring resistance at these low values is difficult with standard multi-meters but, with the right equipment, measuring current would be more accurate.

A genuine 2 ohms at 12 volts DC should show 6 amps but typical multimeters max out at 10 amps so its internal fuse would probably blow if the coil is internally shorted. Note that only a rapid change of input voltage would create the 20,000+ volts required at the spark plug so static DC tests cannot replicate that. The coil is not designed for continuous DC supply so it will overheat if 12 volts is applied for too long.

[steve campbell]

The coil is essentially a transformer where the input is high current - low voltage and the output is low current - high voltage. The high current on the twelve volt side should be measurable by briefly applying 12 volts and if massive current indicates a dead short its faulty, if there is no current its faulty. Measuring resistance at these low values is difficult with standard multi-meters but, with the right equipment, measuring current would be more accurate.

A genuine 2 ohms at 12 volts DC should show 6 amps but typical multimeters max out at 10 amps so its internal fuse would probably blow if the coil is internally shorted. Note that only a rapid change of input voltage would create the 20,000+ volts required at the spark plug so static DC tests cannot replicate that. The coil is not designed for continuous DC supply so it will overheat if 12 volts is applied for too long.

Sorry but that's way beyond my level of understanding...so are you saying that the readings from my multimeter are not really worth much in a diagnostic sense?

[roadster]

Sorry but that's way beyond my level of understanding...so are you saying that the readings from my multimeter are not really worth much in a diagnostic sense?

What I'm suggesting is that it may be helpful to test the 12 volt side of a coil by connecting it to a twelve volt supply and measuring current using your meter rather than resistance. But you need to understand how to use the 10 amp sockets on your meter together with the ten amp dial settings. Being aware that if the coil is internally short circuited the current would blow the fuse in the meter it would be wise to first try without the meter in circuit by flashing the connection and making a judgement without melting anything. Perhaps if you are not confident about this it might be unwise to try it but on the other hand you might learn by your mistakes, I certainly did and still am!

[REW]

The micro switch on the left brake (Silverwing) is a double action switch which requires to work to complete the starter circult. I made up a wire connector to bypass it. Think its the same point of failure on the Burgmans.

This is what I was getting at when I mentioned the rear brake lever switch. I didn't apply it hard enough in my first few restarts when I got the Forza and of course it wouldn't start. Thought of all sorts of problems but it was just this. One can hope eh?

[steve campbell]

UPDATE

New coil arrived today £17.95 from Square Motorcycles

I was dubious as the new coil only read 2.8 ohms primary and 22 Kohms secondary (the OEM ones was not much less at 2 Ohms primary)

Anyway in for a penny etc, connected it up and hey presto a good fat spark at the plug, installed the plug, bolted the coil in place and it started first touch

Many thanks for your help and support

Steve (on the road again)

[steve campbell]

Update update

not so soon....

bike starts and runs fine but exhibits all the signs of a duff coil once warmed up.....v frustrating

[Andym]

Clucking bell (or rhymes to that effect), that's really frustrating.

The £17.95 coil is maybe not the highest quality? Maybe check the charging voltage now it starts before sending it back or trying another though? Did it come with an HT lead and cap or is it the original?

Andy

[steve campbell]

Clucking bell (or rhymes to that effect), that's really frustrating.

The £17.95 coil is maybe not the highest quality? Maybe check the charging voltage now it starts before sending it back or trying another though? Did it come with an HT lead and cap or is it the original?

Andy

it came complete...

i've now ordered a geniune one from my local suzy stealer

Incidentally they were cheaper than fowlers

should be in stock next week....fingers crossed