Wiring the old SS

Just spent a very satisfying day making a fancy new wiring loom for the SS. The old one had melted and the promised improved loom bought at some conciderable cost from Italy was identical- so presumably was liable to melting as well!. So (while ducking as Mr R throws a load of I told you so statements at me) I decided to embark on the great adventure of making my own desighn of loom. So far so good (but then it is my job- be it on trains!) I’ve even taken the load that as standard goes through the ignition swith through two 30a contactors and used larger gauge wire, while reducing the amount of wire used. I’ve moved the regulator to under and to the front of the tank for improved airflow and meaning a shorter cable run, as per the Pantah (not that they were any better!) and have replaced the Boshe units with a fancy electronic box that means I can play lap tops with the flash boys at track days- mind you I have not actualy tried to fire her up yet! I’ve replaced the fuse box with a modern jobbie and mounted it where the regulator used to be for ease of access and the extra space due to the lack of regulater means I have been able to invest in a larger battery for those alternator failure moment rides home.

Oh and I also fitted a 916 alternator!

Apart from reducing the load through the ignition switch I am hoping that the relay/contactor set up means that the battery will no longer leak off its valuable electrickery when parked up for a week or so, as it will be physicaly cut off from the bikes electrical system.

I’ve left the standard Nippon Denso coils on in the original water sucking position for now, but that might all change!

I found that the original headlamp had rusted through so have replaced this with a Monster/BMW item, slightly bigger but fits in the gap just right.

Sounds like a bit of a project you’ve got on Keith?
You say yours used to drain the battery after a few weeks, I found out a few months ago that my regulator had been connected backwards for years, this had allowed a small leakage current to pass even with the ignition off and eventualy drain the battery, it’s eaten loads of batteries over that last few years, seems fine now so hopefully it is now sorted out!
Have you checked that the wiring is correct on the DC side, my red was on the C and the brown was on the B+?

I’m on my third regulator now, so hopefully I’ve got it right this time! i’ve been told by a lot of people that it is the regulator that causes the drain problem anyway- hence the extra contactor! I’m hoping this will be the last regulator as well, having replaced the alternator and wiring, what else could possibly go wrong?

Oh and I finaly fitted that plate to convert the clutch to Hydraulic. its still heavy as hell, but at least the cable wont break and I can always experiment with different master cylinders to lighten it up a bit!

Problem now is when I took the old loom off I looked too hard at the frame and I am thinking " could do with being recoated"- does it ever end?

No, i’m still fiddling. Some times with the bevel. Just sorting small oil leak out now after rebuild. My electrics have been fine except for the overcharging and new battery every 3 years. Everything working fine so down for the MOT and the headlight don’t come on, looks like the switch so that needs stripping again. Should be running soon though.

Good luck with electrics. Still on original regulator, though I have a spare.

Quite obviously the way I was going I was never going to have the old girl on the road this summer, so I have just done what needed doing (completely replaced the electrics) done a few adjustments, fitted the hydrualic clutch conversion and finaly today, fired her up (first kick!!!) warmed her up by letting her tick over (yes TICK OVER!!!)- and now the best bit stopped the engine, not properly warmed up and re started easily- that electronic box has transformed her manners indeed!

Just a quick spin round the block today as I need to get her MOT done, but blimey, you forget how flamin loud they are- fantastic!!

The frame coating, polishing and painting can wait till the winter!!

Hi Keef,

Ive got a '79 900SS, and have had ongoing problems with the electrics for ages, and with loft conversion and other family stuff occurring over the last couple of years I have neglected her to the point where she has sat in the garage and sulked!

My problem is this, and you seem to have an encyclopaedic knowledge of electrics on these beasts, I thought you might be able to offer pearls of wisdom…

On my way back from passing the MOT a while back, and the battery goes flat. Fortunately I was within striking distance of home. As I am a complete numpty with electrics, I blundered around with a multi meter and ended up buying a RR50 rectifier, which didn’t have the desired effect. After much hassle, I then bought a used stator and have installed that. Also a new battery.

So far this is the picture: no GEN light showing, the indicators only stay on instead of winking. However, I am waiting for a new can of oil to be delivered so I haven’t fired her up yet, but I have my suspicions… I suspect that the indicator at least should show some signs of life and the Gen light should come on.

Can you give me some guidance as to how I go about testing for faults? I repeat, me + electric = “duuuhhh”, although I have completely rebuilt in the past. (If it moves, I can understand it!)

Many thanks and eternally grateful if you can help.


Bit hard to say without seeing it really. But if the engine is not running and the indicaters are struggling to flash due to lack of voltage its usualy a flat battery- get some oil in it and start her up- see what happens! If memory serves me correctly you should be getting a steady 16v at the battery when the engine is running. As for the Gen light, mine never worked anyway untill I rewired the bike. what state is the wiring loom in? when I had a peep inside mine the wires from the regulator had obviously overheated at some time, which is a surefire sign that its probably no better deep inside the loom!

chances are your new battery has goine flat as they tend to leak off through the regulator. Pantahs are the same. Mine does not anymore as I put in a contactor that switches the load side of the regulator off when the key is removed.

shame you are no ware near Didcot (if you were we would know each others neibours by now!)


Thanks Keith!

Oil due this week - I’ll give it a go, although the battery is brand new.

Hmmm. I wonder if I could get to Didcot from Cardiff on a full battery… :slight_smile:


So far: I have decided to try re-installing the RR51 reg/rec, and run into the same problems as before:

All OK apart from slight confusion with the white connector and what to do with the old red wires from the battery: I have used the diagram on the ducatisti.co.uk forum which is clear but not quite the same as mine.

  1. I have a bunch of a red, brown and red/white wires one of which I guess goes to the GEN light via fuse box. Do I use brown, red/white or red? I have the owners manual with wiring diagram, and the colours don’t match up although I have no reason to believe any major rewiring has been done in the past as it all seems original. Incidentally, I have plugged in the white to all three at some point and cannot get a spark or any other response for that matter. As I said before, teh GEN light doesn’t work - I wonder if there is the problem between battery and charge light and if so, how do I track it down?

  2. What do I do with the old red/black wires from the battery? The red goes into the fuse box, but shares a spade connector and I am reluctant to mess with this.

I fired her up at the weekend, but want to get the electrics fully sorted if I can.

Sorry to be somewhat verbose - I’m trying to include as much info as poss.