Dommie wiring

Hi Pete,It all depends on what switch you have and whether the bike was wired (and is still wired) for Mag or coil ignition. If you intend to stay with the Mag (and I would!) then a bike that was wired for coil ignition and PRS8 switch may not need the complicated wiring that the charge system needed back then. IF you have a modern or zener regulator you could simplify the wiring and still use the PRS8. There could be an issue with overpowering the system if you have a new efficient alternator which now does not power the ignition. An old alternator may not be a problem. ..You could fit an uprated control if there is overpowering.I expect Al will chip in soon.

THe PSR8 was fitted to all coil ign bikes ,it is a complex switch with 2 layers of contacts . Google it.I would think is very likely yours started off with coil 99c engine code??, and someone fitted a mag. Did the same myself once.

HELP, I am confused, My 1959 600cc Norton Dominator 99 has an Alternator, Rectifier, Magneto and a 6 Volt battery and I have a copy of the unnaproachable Norton instruction/Maintenance Manual, the nearest electrical diagram is the one for (500 S.S., 650S.S.and 650 American) but the fittedlighting switch is not as shown, if it was, Istill could not follow the connections as shown in the Switch Rotor Positions. If possible I would prefer not to change the switch.

Anybody out there any ideas.

here's hoping Pete

Hello if your looking in haynes manual with this bit wrong, your machnie has the Prs8 lighting and igntion switch for coil igntion , the 500ss 650 Manxman 650SS were the SA41 switch, magneto igntion, were has from september 1958 the model 99 and from Apirl 1961 model 99ss was Coil igntion So your model 99 has been fitted with a magneto at some time by one of its owners the right igntion switch sould be a prs8 igntion /lighting switch, to up grade altenator use RM21 or Rm 23 lucas alternators two wires, has there 12V you need a solid state rectifier

yours anna j

Hi Peter, If your switch is glued in (that was done to PRS* switches when the plastic threads got chewed up or cross threaded ) then you may find it awkward to access all the connections.I would not bother with a poor quality pattern replacement . If you can access the connections or re-glue it ,you can make a few wiring changes and finish up with a system similar to the Mag SS bikes or even change to the SS switch. I would change to 12v anyway and a modern regulator and use your switch. I did that but still use a 12v coil with a Zener Diode and solid rectifier, What does your bike resemble ? a later SS ?.Its not necessary for the charging system to connect to the switch at all ,Are you keeping the ampmeter?.The orriginal wiring was most likely as the 88/99 std and Deluxe. I reused all mine as it was better wire than the new flimsy stuff, You will need to study the switch and understand its inner working to simplify the system and remove the alternator charge switching function if convering to a modern system,There are diagrams for the switching ,it is a big beast of a switch. To help you we need to understand the direction you are going and the look you want .Sticking with 6v and switched control you may still find the battery gets too much charge if you ride far and fast but a 6 v reg could be added. If you always run with lights on it will make a difference. Lots of choises.To keep changes really simple ,reconnect as std and run daytime with bigger lights on , Change the old rectifier though !.Some of the coil system diagrams have a small error in the link wiring diagram .

Its what we said was the most likely, a 99c which denotes a coil ignition system with an 18D2 distributor, These were disliked by many who were happy to swap in a magneto. This was all good except it left the system with a higher rate of charge than needed which would stress the battery and blow acid over the nice shiny silencers.There were some in period "fixes" for this, We now have more options for charging control these days.To my mind the most desirable dommy ever would be an 88/99 ss with the splayed twin carbs ,a mag!! and the green/dove grey finish, And you are closer to that than me!.

Its what we said was the most likely, a 99c which denotes a coil ignition system with an 18D2 distributor, These were disliked by many who were happy to swap in a magneto. This was all good except it left the system with a higher rate of charge than needed which would stress the battery and blow acid over the nice shiny silencers.There were some in period "fixes" for this, We now have more options for charging control these days.To my mind the most desirable dommy ever would be an 88/99 ss with the splayed twin carbs ,a mag!! and the green/dove grey finish, And you are closer to that than me!.

Not 100% sure what you have but some Lord Lucas 'Prince of Darkness' food for thought............

Rgds Steve

Hi Peter - you say you described the switch in an earlier message - not on this posting you haven't. It would be easier to send a photo. A PRS8 has a large base "ring" with two rows of screw-fixed terminals for the wires and it has a karge dome-shaped black plastic (Originally Bakelite) switch with an ignition key slot in the centre. Back in the 1960s I changed my coil ignition to magneto - usingthe K2F from my 1955 '88' - and I changed the PRS8 switch for an 88SA. I intend to change it all back to original for concours!