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Found the issue.
Thanks for the input guys,.
As suspected I had some earthing issues. While trying to fix this the bike stopped being able to start.
The earth from the ignition module was so corroded where it met the plug to the loom that there was no continuity.
Then I found the 2 old style fuses under the rear of the main frame had the same issue. This fixed all the lights.

I'm going to need to pull apart every connector and replace.

You will want to replace those fuses with proper automotive blade fuses. Otherwise you will be constantly fussing with their continuity.

You also want to renew the heatsink paste on the ICU. Any electronics store will have it. It is used in PCs.

Check your coil carefully to see if it is the original. If it is, it will probably need replacing due to cracking. How long did the PO own the bike? He may know.
But the cracks will appear around the end. If the coil gets wet, you will stop.

It would not hurt to replace the spark plugs, caps, and wires.
My go-to guy was always MikesXS (sells stuff for XS650s). Good wire, cheap, and the NGK caps I love.

If you do still have the original BMW wires, do not throw them away without first removing the soldered-on end caps that go into the coil(s). You can de-solder them and reuse them from now until doomsday. This is the best way to connect your wire to the coil. I don't know where you can buy these caps.

Thanks for all the info Rob,
I've already replaced the coil on the bike, first thing I did upon buying it not running. leads and plugs are all good.
Plan on replacing fuse box already with a new style box.

I don't understand what you means about the end caps to the coil and reusing them?
I replaced the coil with a Harley replacement coil for about 100000th the cost haha. It has a screw on terminals on this coil.
I've crimped and soldered on ring terminals for this.

I've got a big box of plugs etc so tonight is going to be sitting in the shed with a few beers and redoing most of the bikes elec system.

Thanks for your help again.

neillh wrote: I don't understand what you means about the end caps to the coil and reusing them?
I replaced the coil with a Harley replacement coil for about 100000th the cost haha. It has a screw on terminals on this coil.
I've crimped and soldered on ring terminals for this.

These are the end of the high tension leads going to the sparkplug. They push into the coils with an interference fit.

Normally, auto parts stores sell the crimp-on style with a single "tooth" going downward into the center of the H-T wire.
They look like this:


With the soldered-on ends, you strip back part of the insulation on the new wire, feed the wire through a hold in the end of the "end", and solder it on.
I wish I could find a picture of that, for you.

Ah, sorry I didnt know you meant the high tension leads.
They still have some years life in them and dont need replacing. (Dont look standard anyway)
I thought you meant the 2 wires going to the coil from the ignition module.

For neillh and my ol' bud Rob: Steal these pics for your files, Rob!

First photo shows HT ingntion wire poking through the end cap. Second snap with wire strands spread out and soldered to the cap. Finished up by crimping the sides into the wire sheathing.

Found a package of assorted terminals at an older auto parts store. Take your sample with you. Most of the younger clerks in the newer FLAPS just respond to your request with, "I ain't never seen nuttin' like dat." Find an old school guy.

So will somebody please explain what it is about bad grounds that encourages electricity to go in directions it wasn't intended to go? Obviously the current is seeking ground, and when the intended one isn't working it goes someplace else. But if it can go through the other, wrong routes, why doesn't it do that all the time?

enigmaT120 wrote:So will somebody please explain what it is about bad grounds that encourages electricity to go in directions it wasn't intended to go? Obviously the current is seeking ground, and when the intended one isn't working it goes someplace else. But if it can go through the other, wrong routes, why doesn't it do that all the time?

Because current will always take the easiest route and a good earth will be close to zero ohms so the current will flow that way rather than through the higher resistance of say a bulb. Even with a good earth you could construct an augment that it also goes via undesirable routes but any current flow would then be minuscule.

barryh wrote:

enigmaT120 wrote:So will somebody please explain what it is about bad grounds that encourages electricity to go in directions it wasn't intended to go? Obviously the current is seeking ground, and when the intended one isn't working it goes someplace else. But if it can go through the other, wrong routes, why doesn't it do that all the time?

Because current will always take the easiest route and a good earth will be close to zero ohms so the current will flow that way rather than through the higher resistance of say a bulb. Even with a good earth you could construct an augment that it also goes via undesirable routes but any current flow would then be minuscule.

Right. All those other paths that cause the freaky behavior have a load (or two) between them and the ground, thus the intended path to ground being so much lower in resistance.

enigmaT120 wrote:So will somebody please explain what it is about bad grounds that encourages electricity to go in directions it wasn't intended to go? Obviously the current is seeking ground, and when the intended one isn't working it goes someplace else. But if it can go through the other, wrong routes, why doesn't it do that all the time?

The answers you've received are correct. When you attend an electrical class one of the first things that is introduced is Ohm's Law. You've heard of it. In formula form it goes E (voltage) equals I (current) times R (resistance). You've seen the equation: E=IR. (E is commonly stated in units of volts, I is commonly stated in units of amps, and R is stated in units of ohms.)

Knowing two of the values you can calculate the one you don't know. You can rearrange the same equation in different forms. When you don't know the voltage you can get it by multiplying I (current) times R (resistance). If you know the volts and the resistance you can calculate current with the equation rearranged: I=E/R or amps equal volts divided by ohms. If you want to calculate the Resistance you can rearrange the equation to R=E/I or volts divided by amps.

In a typical grounding problem a corroded connection creates a high resistance where there is supposed to be a very low resistance, that is for all practical purposes, zero. in the equation calculating amps (I=E/R) because of the bad equation the resistance goes from near zero to a much higher resistance. Thus in the equation I=E/R the resistance will go from much less than one ohm to much more than one ohm. The higher the R value, given the same voltage the less current will flow. In a grounding situation the R value is supposed to be very low, approaching zero. But the higher the resistance from the corrosion is the less the current becomes (with voltage being the same in both cases).

Probably what I wrote will be confusing. Since you're going to be playing around with airheads you're going to encounter electrical problems. You might consider going onto the internet looking for information on basic electricity. You will eventually stumble onto a site which teaches in an approach that works for you.

Once you 'get it' you will feel empowered.

Pep talk over.

Ken