still not starting

[Barnsey]

Yeah,  I measured the resistance, battery to the coil and it was around 1 ohm on both sides, so, could be worse.  We tried kicking in the emergency position of the switch too, but no joy even though we had sparks in both positions. 

Weirdly the lights won't work when powered from the battery, only if I substitute a bench power supply, so maybe the battery is a little tired.  Any recommendations of a good battery to go for? 

I've been looking at the wiring diagrams. Does anyone know which pins connect together on the ignition switch?  Not easy to understand in the diagram, either Hayne or Rupert Ratio.
The loom is clearly labelled as being up to 1963, but I wonder if there might have been any variations. 

My thought was to bypass the ignition switch and ammeter but I want to properly understand what needs to connect to what before I pitch in. 

[rhyatt]

So you get a spark in both positions , good
Various posts seem to indicate the battery voltage is weak , try starting it with the battery charger connected and switched on , the ignition (if you're on 6v still) , will pull about 4 amps which will quickly kill a tired battery.
Battery , look at Tayna batteries , good prices and delivery.

[Barnsey]

Okay, I have ordered a Motobatt from Tanya, thanks !

[neil1964]

I would try a jury-rigged live direct from the battery to the coil (disconnect the loom wire from the coil). This will make sure you're getting the full voltage there. 4-5 volts is very low especially with a fully charged battery.

Have you done this simple thing just to get it running to prove that everything else is ok?

[Barnsey]

Yes, I had tried that but without any joy.

I've also tried kicking over with the battery charger (4A) connected, but the battery quickly dropped to 4V. 

Buzzing out the loom against the diagram in Haynes hasn't revealed anything.

The ignition switch buzzes out OK too.

  Maybe I will be waiting for the new battery.

[Barnsey]

Does the metal case of the coil count as a connection to + ?  Right now I have 10 ohms between the can and battery +, so, maybe a link wire to the battery here would help? 

[iansoady]

It definitely sounds as though either the battery is dead - your new one should eliminate this possibility - or that there is a partial short circuit somewhere draining it. When you tried my suggestion did you remove all other connections to the battery and coil?

The 10 ohms between coil casing and earth is by the way - it won't really affect anything. Have you checked what the current is between battery & coil when the points are (a) open - should be zero - and (b) closed - should be no more than an amp or so.

[rhyatt]

The outer can or body of the coil should not connect to any of the coil connections.
Either the 2 small primary connections or the central ht connection.
Basically, the voltage , negative volts , go battery , switch , coil neg , through coil primary , out coil pos to points , along the points wire to the points and to earth at the points.
Making and breaking points create and destroy the magnetism in the coil.
The dying or collapsing magnetism creates a high voltage , 12 or 15000 volts in the HT side of the coil.
The spark whizzes along the htlead through the plug and back to earth through the engine to chassis to battery earth positive.
It doesn't rely on the coil can or body.

[Barnsey]

Thanks for all of that.

  With the coil connected and the ignition on the ammeter indicates around 2A, and the battery voltage rapidly drops below 4V.  If I disconnect the col terminal the voltage goes straight back to 6V.

  I'll try out the bypass lead which I made up again. 

[Barnsey]

Just to confirm.  I measured the current through the coil and it is 2A on my multimeter, with the points closed. 

What is slightly odd is I am supplementing the battery with the battery charger, which is rated for 4A, but the battery is still sagging. 

Resistance between the coil and ground shows open circuit with the point open and closed circuit with them closed, as you might expect.

   It all seems to be pointing in the direction of a duff battery.

[rhyatt]

I think youve just proved it.
Ignition on and points closed (so the battery goes to earth via coil primary and points).
Is tantamount to a straight short to earth.
Obviously as engine rotates and points make and break the short to earth is momentary.
How long are you leaving it connected before voltage drops to 4v ?
Get your new battery on and see how you go
as a matter of interest , how old is the current battery??

a 6 v coil is about a couple of ohms across the 2 primary connections + and - (remove everything else when checking)
and from 1 of these primary connections to down inside the HT connection is around 4k ohms give or take

[Barnsey]

Sorry I have no idea how old the cyclones are as they came with the bike. 

[iansoady]

A typical bike 6v battery would be about 8 amp-hour rating, in other words will supply 6 amps for an hour (or 2 for 3 hours). Definitely the battery from the readings you've provided.

[scifi]

Sorry to hear of the ongoing problems.  Lots of things you tell us seem to make no sense.
 
For example... The coil case to ground being 10 ohms, is neither grounded nor open circuit, but somewhere in the middle...  Almost like an internal fault to ground, caused by a partial contact to the coil windings.   
I know this won't help much, but my R.E. Bullet coil case is not connected to ground, even though it is clamped to the rear mudguard.!

The other strange thing is that you say the battery voltage sags even with a Battery Charger fitted, and that the lights go dim from just the battery.  Maybe as the voltage is going to 4v, that could suggest only two cells of your battery are good.

Maybe a push down a hill by two strong lads, whilst in second gear, would get it going..  Best of luck..

[Barnsey]

Yep.  I am confused too.  The more I find out the less I seem to know.