3 phase alternator upgrade

Can you take a photo of the alternator, reg/rec and wires inbetween. I,m struggling to understand your description!

Mark,

The regulator/rectifier should have five wires, three for the alternator stator (possibly all yellow), and  the other two might be black and red.

Hi Mark

Have you bought a new regulator/rectifier to go with your three phase stator? You must have a three phase regulator. I think you are trying to connect your old two wire regulator? or have I missed some detail?

Norm

Sounds a bit like the previous owner rewired and decided to use twin core for each alternator lead. I used a doubled up wire to connect battery to earth because I didn't have a big enough single. Since it sounds like you have four wires to do the job of three you should be OK but only if the wire size is big enough to carry the current.

Your photo 1 shows the old two wire alternator connected to the wiring harness

Your photo 2 shows the  wiring harness to the original plate rectifier.

You need to study the wiring harness diagram, understand where all the relevant wires go and see what wiring can be reused.

A photo of your new components would be helpful.

fitting a 3 phase alternator and a modern Reg/rectifier tidies up the wiring somewhat as actually there are less wires involved to fewer components I.E. two components to connect as against four with the original system (alternator, rectifier, and the two zeners)

Thanks Mark, I now understand - you have shown the old two cables for alternator and rectifier, but have a three wire stator and regulator you want to fit.

I think the reason you see pairs  is because there will have been two pairs (WG and GY?) connecting to the alternator and then splitting to the old rectifier and zener diodes. We need to check Mark that the zener diodes have already been removed by a previous owner and a COMBINED regulator/rectifier fitted. Or, if the zeners are still fitted to the footrest plates then you need to do some more substantial rewiring - essentially three new cables connecting alternator to new three phase regulator (can be yellow), new regulator earth (red) and live feed (brown/blue) connecting to a fuse and then the battery, and remove the old zeners and rectifier. You also need to work out where to mount the regulator.

Cables are normally rated in cross sectional area, which is not simple to visualise. If you cut away the insulation from an end then a 1.2mm diameter (1mm sq area) copper cable bunch is about 16amp (lights, etc.), 1.7mm (2.0mm sq) is 25amp and 2.1mm (3.0mm sq) is 33amp. The 1.7mm diameter will be enough for each of the three phases, while the 2.1mm diameter is best for connecting the regulator to battery, earth and then fused at 25amp.

I have rewired a few bikes but I am only an amateur and anyone else is welcome to have their say.

First, understand what your new system will make redundant, you'll be surprised how many connect a modern rectifier regulator and still leave the zener connected. 

Once you have established the above then wiring in the new system will be easy. If the stator is a new Wassel item it will not easily fit a MK3, the old LAP version fitted nicely. 

You might need to space it out a bit, but check the outer chaincase will fit. If the stator fails Wassel will not warranty it when used on a MK3. 

Using a RM23 stator, mosfet rectifier and BSM, makes the 3 phase upgrade redundant these days. With Tri Spark ignition it will start with the battery disconnected and no blue capacitor either. The BSM shows green on tickover, the old rectifier in the same setup could not even do that. It makes efficient use of what the RM23 stator outputs, and keeps a 14Ahr battery well topped up. 

The cables in a traditional Commando loom are 8.75A (call it 9A) 14/030. You can use 'modern' thin-wall which says it will carry more current but in fact it carries the same current but the thin wall runs warmer hence does not melt as soon as the 9A cable does.

The two wire we see here are to the Zeners on a MKIII as the Zeners are on the AC ie alternator side of the rectifier. Yes it would be ok to split one pair out to get three wires BUT do make sure you spilt out both end of the same wire. Also running three new wires from the alt. to the reg. would be a better job.

Any further questions give me a call 01953 884681