still not starting

[Steve.S]

Unfortunately, your new battery is flat.
A 6V battery reading 6V is considered to be 100% discharged.
When it reads 6.4V it is 100% charged.
However, I'm sure this is not a problem. You simply need to charge it up. Make sure it holds 6.4V for a week or two.
I wonder if you could make up a packing piece for the coil bracket from a bit of scrap alloy, or maybe some strips of old inner tube?
This needn't concern you for the time being, but an AGM battery is not necessarily ideal for an alternator with switched coils and no zener diode. They prefer electronic regulation. But if your luck is anything like mine, the alternator won't work anyway.
Let's just get the thing running first.
 

[Barnsey]

Okay.I am sure that the AGM was not fully flat, but I have put it and also the old twin cyclons on charge.
I will see if they are still holding charge when I come home from holiday next Thursday. 

The new, non-resistor cap has arrived so I can try that out too. 

The new, bigger coil turns out to need a thicker lead too, around 11.5mm vs 8mm, so I opted to order the correct coil. I might return this one, we will see.   

[rhyatt]

I wouldnt leave batteries on charge for a week
overnight is fine , but not sitting there on their own all week on charge

[iansoady]

Yes if an old fashioned charger, but a modern intelligent model would be OK.

[V500]

In theory, but not in practice. I personally know of several batteries that failed too quickly by being left connected to maintenance chargers, Optimates and Lidl's finest battery chargers.
When Tayna were contacted re the failures they advised against long-term connection.

[Steve.S]

I think this talk of wire sizes is becoming unnecessarily complicated. You just need to connect a feed wire to the coil.
However, to complicate matters even further, if you mean what is commonly known as 11.5mm squared, this would be starter cable capable of taking about 70 Amps. If you mean 11.5mm diameter, much the same would apply.
The largest cable I would use would be termed 28/030, 2mm squared, and will take up to
17.5 Amps. This is about 3mm diameter. Otherwise, just use what I would call normal cable (14/030, 1mm squared) which will take up to about 9 Amps.
Your coil should draw no more than 4 Amps, hopefully less.
Was it a Mr. Faraday who told you to use 11.5mm cable?
I don't remember coil feed cable being particularly large.
For the time being, just connect a bit of wire and try to start it. Bear in mind, if it kicks back, it's probably over advanced (just turn the "distributor forwards a bit). It would not be good to break your ankle just before your holiday.
Hope you have a good one.
   

[iansoady]

In theory, but not in practice. I personally know of several batteries that failed too quickly by being left connected to maintenance chargers, Optimates and Lidl's finest battery chargers.
When Tayna were contacted re the failures they advised against long-term connection.

The original question was up to a week which I think would be fine. I don't leave my batteries on permanent charge but refresh any on bikes I'm not using with a couple of days with a CTEK charger.

[iansoady]

Also, re wire sizes: I use 1mm sq thinwall cable which is rated at 16.5 amps for everything on older bikes. The most you would see anywhere is about 10 amps from the alternator if it's running at full whack.

These cables are available from VWP as well as my preferred supplier (as they're round the corner from me) ALM. https://www.almsolutions.co.uk/index.php?main_page=product_info&cPath=3_60&products_id=42

ALM also have bullet connectors etc.

[V500]

I do too. Easy to use when inserting through sleeving etc and more than adequate in it's rating.

[Barnsey]

Non resistor spark cap fitted.  The spark still looks pretty weak to me, and inconsistent. Not sparking on every kick.   I now have the right coil to try in, but it came without the HT spike to go on the end of the lead.  Now on order from the nice chap at Kidderminster motorcycles. 

[rhyatt]

Short term fix.
Use a scalpel to trim off 1" of ht sheathing and spread the copper wire out into a ball when you poke the lead into the coil

[neil1964]

Short term fix.
Use a scalpel to trim off 1" of ht sheathing and spread the copper wire out into a ball when you poke the lead into the coil

Always did it that way!☺️

[rhyatt]

when I do have the brass clip thing, I always solder the copper to it

[V500]

Sometimes that seems to make the acorn too "tall" to get more than a thread or two into the coil terminal, I find.

[Barnsey]

Right, I've fitted a new coil, spark lead and non-resistor plug cap.  The spark is looking more reliable, although I haven't persuaded it to jump more than 4mm.  I used a shiny new HT spike on the lead and I soldered it on just for good measure.