Honda-SOHC

I suspect you could use the  Synthetic technology type - I think they mean semi synthetics!

Today I cut the spokes out of the old wheels with my mates  angle grinder - point of no return - I will now  need to have them rebuilt in the colour of my choice - not Nut Brown not available - might treat myself to Gold Anodised Alloys - undecided atm. I have plenty of time to save up and keep CWC in business. 

The front hub was pretty much as it should be - the rear hub had a number of spoke rub marks on both sides of the hub.
What causes this to happen?

You could have polished it Matt 

I think that is an accidental Oxymoron Ken.

Bike looks nice with trendy holes in the disc.

I'm not familiar with 6 volt systems - do you have a manual for the voltage outputs? The lower reading looks sensible the upper readings might be tad high. That said if they are flashing at idle is that relevant.
Might be worth fitting an extra condenser at the coil end to reduce interference.

This series was my mentor on the 400 - some gaps in detail but was a real help.
I switched on the captions and would pause at what seemed like complicated stuff.
When unsure I would post pics & ask here - yes some jokes but the feedback from a handful of members was invaluable.

https://www.youtube.com/watch?v=NQgwhv8v6Os

Thanks Brian I'll give that a try tomorrow.
Ted I have used 2 relays , both new and different makes with the same result.

Yes but are they the correct part you have fitted?

As someone here has posted earlier if you bridge those two wires (not the earth) can you make them flash on and off by breaking and making the connection the connection? If it's yes you know where the answer lies. I'm not great with electrics and have no idea how a two terminal flasher really works but it does.

I still think it's the bulbs - a few years back I fitted LED DTRL's to our previous Jeep. As soon as there was a hint of rain they would start flashing or fail likewise with LED  festoon bulbs.
IIRC some LED bulbs are rated as 12-24 volts as the operating range  some are not polarity sensitive.
They have improved in quality & reliability but still a lot of duff ones about.

This might sound basic but are you sure the flasher units are the correct ones for your total bulb wattage & designed for a negative earthed vehicle?

When I replaced the flasher unit in my 400 I could not find the ones with three terminals so fitted a two terminal unit.

I am thinking  that you might have the later car type flasher unit they will be marked with an earth designed for modern cars that are positive earth.