Electrical help needed

[stidds]

Oh God I hear you groan.

I have a 1978 CB550K which I am rebuilding.  I have finally gotten to the dreaded wiring and I am having a real problem.

I have put a new battery on, and wired everything up as per the Haynes manual, however I have no life.

I have a new battery, and I have used a multimeter to trace the current.  The red cable at the ignition switch is live and when I put the key in the P position the brown wires have current and will light up the rear light.  Problem is that when I put the key in the On position I lose all power (even to the red cable).

I have looked at the ignition itself and it looks fine, I have even quickly directly wired the red cable to the black cable at the ignition switch and again I lose all power immediately.

Can anyone give me a direction to go?

Thanks



Sean

[K2-K6]

Try metering the black cable (if that's the power route into the loom) disconnect the battery and see if the black runs to earth with a continuity check to see if it's plugged wrongly somewhere. If not running to earth then try to find where it is going to make sure it's connected to something sensible.

Check main fuses are ok and meter through to the entry and exit wires of the fuse box.

Do you get any lights on with the ignition or nothing at all?

See what you get and post again for others to see if you get nowhere.

[stidds]

Will do many thanks for your reply.

Just a quick question though, after looking at the loom a bit more some of the dodgy wiring is very thin wire, it looks like 5amp cabling (I have some that I used for comparison).  Would this cause the problem?

[mickwinf]

i also have a k3 which was off the road for many years and when i fitted the new battery nothing much happened.i found that the fuse connections were not good they must be absolutely spotless, also dont forget the earth wire that fastens on the coil bracket, make sure it has clean metal to earth to.Another issue i had was one of the block connecters behind the fuse box was dirty and if not yet fitted it interupts the earth.Hope you get it sorted, electrics can be a nightmare! Actually i may have a spare loom in my shed,think it maybe a f1 though.Cheers, Mick

[stidds]

Thanks for your reply Mick, that is excellent advice I will start checking the connections.

I think the 1st job is to take the loom off of the bike, remove the tape holding it together and see what I have and where it goes.  That way I can do some continuity testing of the cables.

I will get a supply of good quality wire and replace any bad parts.

[K2-K6]

Stidds, your question about wire gauge; I think the rating was ok but may not be much spare capacity although it seems not to give a problem. Most of the issues I've seen come from damage or corrosion and they seem to function reliably if you take care of these points.

If the size gets much bigger you will have difficulty in threading all around any tight spots and have to squash it in which can get you struggling particularly the headlight.

Another higher wear point can be around the headstock especially if the covering has been damaged.

[Spitfire]

When I rebuild my F1 I took the harness into the garage and cleaned every connector with my Dremel and a tiny wire brush, small files, sandpaper, lots of WD40 and all sorts of odd tools. When everything was shiny I put the harness back on and using Dielectric grease  connected everything up. However I still had a problem later with the soldered joints on the back of the fuse box failing which gave me an intermittant no power problem.

Cheers

Den

[stidds]

Thanks for the replies guys it really is appreciated.

I will look at the loom and clean everything as per Spitfires message.

Can anyone tell me what is the best size cable to use on the loom?

[Spitfire]

Don't know where this came from (think it was a thread on the US site) but this was the info that I used on mine, got the wiring from Halfords and the connectors from ebay (Yambits I think).
Think it was from this thread, very useful
http://forums.sohc4.net/index.php?topic=13258.0;nowap
http://forums.sohc4.net/index.php?topic=13258.50
"earth 2.5 mm2(there are a lot of branching from earth)
all other 1,5 mm2"

Cheers

Den

[stidds]

Thanks every so much Den, that link is perfect.

[Spitfire]

Yes it's a very good read and is packed with useful info, I really enjoyed it.

Cheers

Den

[totty]

For wire I've used both of these in the past:
http://www.vehicle-wiring-products.eu
http://www.autoelectricsupplies.co.uk

The thinwall cable is worth considering