Does a coil body have to earth?

[The Other PaulG]

Not GS, sorry, but the terminally static DR600...

Forgive me if this is a naive question, but does the ignition coil need to earth to the frame?

These bikes have a magneto ignition, if that makes a difference.

There are the two LT wires going into the coil from the loom, no problem there.

But to spark, does the charge down the HT lead just earth to the mass of the bike, or does the coil unit need to be earthed to the frame in order to complete the HT side of the circuit?? Logic tells me it should, but I see no way in which the resin coil housing earths itself.

... and I currently have no spark.

Help??

 

[cookie]

don't know specifics of that particular ignition, but usually the primary coil has live & earth connected, then the earth is removed by the points/ignition unit. at that point the collapsing field in the primary coil induces a big charge in the secondary which is connected to the spark plug which sparks.

but...i thought magneto ignitions did not have coils

 

[The Other PaulG]

but...i thought magneto ignitions did not have coils

errrr OK this could explain quite a bit... Maybe it's not a magneto, it's one of these:

The ignition system is one which doesn't require a battery to make the spark, the primary side takes its power directly from the charge generated by the spinning crank.

(This is why you have to give it a real swing on the kickstart to get it firing, and a 600cc single takes some swinging, which is why DR600 owners all have overdeveloped right legs...and why Suzuki replaced it with the electric start 650)

PG

 

[cookie]

the first bit is more or less how it should work then.

i think

 

[The Other PaulG]

Thanks Cookie.

By 'the first bit' are you referring to the theory that the HT current goes down the HT lead and sparks because the mass of the bike is acting as an earth, rather than a physically connected circuit that returns to the coil's secondary winding via the frame and the coil body?

PG

 

[cookie]

Thanks Cookie.

By 'the first bit' are you referring to the theory that the HT current goes down the HT lead and sparks because the mass of the bike is acting as an earth, rather than a physically connected circuit that returns to the coil's secondary winding via the frame and the coil body?

PG

TBH i'm not at all sure how the secondary coil is connected at all

academic since one never actually connects anything to it bar the HT lead.

i just found an article here that may prove helpful.

i believe the answer to your initial question Does a coil body have to earth? is no, except on the HT side.

 

[delpel]

If my memory serves me rightly, there are a couple of coils on the plate inside the crnkcase cover. As the crank spins it induces a voltage through the coils. One coil would be for battery charging (if you had one) via a diode and the other coil feeds the ignition coil or the LT wires (approx 12-14 volts).

The secondary coil of this ignition coil is made of many thousands of more turns than the primary and so steps-up the voltage to many thousands of volts. The output of the secondary travels done the HT lead, through the spark plug and then to earth. The ignition coil is earthed through the laminated windings that hold the whole lot together. The HT side picks up it's earth through the spark plug. This can be seen when you hold the plug against the engine block.

Hope I haven't confused you to much

 

[Timolgra]

Afew years ago I had problems with the secondary ignition on my DR 350. I had the coil rewound by a company called something like Motor Rewinds in Plymouth with a very quick turn around.
I can't remember but think the earth is through the body.

But you are right about kick starting DRs, so......

 

[northengit]

TBH i'm not at all sure how the secondary coil is connected at all

academic since one never actually connects anything to it bar the HT lead.

i just found an article here that may prove helpful.

i believe the answer to your initial question Does a coil body have to earth? is no, except on the HT side.
Thats an interesting link I'll have the spuds out over the weekend....

 

[Bigtwin]

Thats an interesting link I'll have the spuds out over the weekend....

What you and the Mrs do in the privacy of your own home is no concern of ours...

 

[(RIP) Kaister]

primary and scondary coils need an earth - usually thru the body or windings.

think of them as transformers with 2 wire inputs and outputs.

 

[ktmmark]

Sounds like you have an a/c ignition which dose not use the battery for a power supply but a coil on the stator behind the rotor

1/ do you have an ac output on cranking
2/ the engine is stopped by cutting the spark (earths out the coil ) so check all cut out switchs clutch /sidestand /ignition switch
It would help if you had a manual to locate the wires