Britbike forum

Classic British SparesKlempf British PartsBaxter CycleBritBike Sponsor SteadfastCyclesThe Bonneville ShopLowbrow CustomsSRM EngineeringGirling Classic MotorcycleLucas Classic MotorcycleHepolite PistonsIndustrial tec supply

Upgrade your membership: Premium Membership Gold Membership


New Sponsor post
Cyber Monday Sale - 10% off at The Bonneville Shop
by The Bonneville Shop - 11/29/21 5:34 pm
New FAQ post
How to find my own threads?
by reverb - 11/20/21 3:55 pm
Manuals on DVD - Buy 4 for 3
All 4 DVD Manual
Member Spotlight
The Bonneville Shop
The Bonneville Shop
Broomfield, Colorado, USA
Posts: 102
Joined: November 2018
ShoutChat
Comment Guidelines: Do post respectful and insightful comments. Don't flame, hate, spam.
Top Posters(30 Days)
NickL 79
Rohan 73
Top Likes Received (30 Days)
Newest Members
old ion limey, muzz750, Motorcycles and Art, SteveDee, Gus_Carrero
11,924 Registered Users
Who's Online Now
0 members (), 28 guests, and 21 robots.
Key: Admin, Global Mod, Mod
Previous Thread
Next Thread
Print Thread
Joined: Aug 2021
Posts: 2
S
Novice poster
OP Offline
Novice poster
S
Joined: Aug 2021
Posts: 2
Hi everyone, I'm new to this forum and this is my first post so please bear with me if I'm missing the obvious and sound stupid.
I’m in the final stages of rebuilding a 1965 T120 (engine No DU24627) and I’ve hit a problem. After refitting the engine into the frame, I’ve realized that sometime in the past, the wires from the alternator stator to the main wiring harness have been replaced but not colour coded, i.e. they’re all the same colour. These should connect with bullet connectors, to the main wiring harness wires, coloured green/yellow, green/black and white/green.
The bike was, I think one of the first to use a 12 volt system and originally had two 6volt batteries wired in series to give 12 volts. The alternator could supply either a 6volt or 12volt system. When using a 6 volt system, I believe the alternator output was regulated, by switch positions of the lighting and ignition switches, to prevent overcharging the battery. When used on a 12 volt system a zener diode prevented over charging the battery.
The alternator stator is the original (Lucas RM.19) with exposed windings, not the newer resin encapsulated type.
I don’t want to guess which wires to connect to the main wiring harness and risk “cooking” components when I run the engine.
Does anyone know a way I can test the alternator output cables so I can identify and mark which wire connects to the correct coloured wires of the main harness or does anyone have a photograph which shows the original coloured wire connections at the stator so I can compare with my set-up.
Any help or advice would be greatly appreciated.

SmallpersonPete

Triumphs on eBay
Joined: Aug 2001
Posts: 1,988
Likes: 60
Britbike forum member
Offline
Britbike forum member
Joined: Aug 2001
Posts: 1,988
Likes: 60
Pete, I'm sorry I can't help you with an answer to your questions, but... and this is no way intended to be a smart-ass reply... I would look at this as the perfect justification to replace that brittle old open-faced stator with a new encapsulated version.

Joined: Sep 2013
Posts: 3,440
Likes: 156
Q
Britbike forum member
Online Happy
Britbike forum member
Q
Joined: Sep 2013
Posts: 3,440
Likes: 156
are you planning to use it at 12. volts ?

as the 3 wires have lost the color coding you will have to
do some experimental pairing to determine the best output .
this is pretty simple
you can run the bikes ignition off a battery ... while volt testing , or load testing ... the stator leads .

if the 3 wires are going to used for 12 volts ... you "cant" hook them up
wrong and hurt anything ... so this is good news ... but only one pairing will give the best output .
all 3 wires will output AC ...
number the wires 1,2 3 .

pair wire 1 to 2 ... run 3 alone ( as the green white ) ... open volt test the 2 wires ( or run a headlight as a load )
pair wire 1 to 3 ... run 2 alone ( as the green white )... volt test ( or volt test under load )
pair wire 2 to 3 ... run 1 alone ( as the green white ) ... volt test

these 3 pairing output tests
can be done at relatively low RPMs ( and voltage will increase with RPMs )
... simply pick the wire pairing with the best voltage output .
the best pair will be equal AC outputs ... so either wire can go to either rectifier AC input .

Or buy a new stator and rotor ... if you want to run a decent headlight .
the newer stuff will bolt right on .
I dont mind messing
with the old open stators , but its not always that straightforward are productive .

Joined: Nov 2012
Posts: 2,283
Likes: 104
K
Britbike forum member
Offline
Britbike forum member
K
Joined: Nov 2012
Posts: 2,283
Likes: 104
If you have a decent ohm meter, test resistance between each pair.

One pair will have the highest reading. Mark the other wire White/Green.

Now test the 2 wires against that W/G.

One will be lower resistance, that will be G/B

The higher resistance to G/W will be G/Y.

The understanding of this is that the G/W is common to all the stator coils, and should be a sole connection to one side of the rectifier.

The G/Y is from 2 pairs of coils (high output)
The G/B is from 1 pair of coils (low output)
Any routes of these must go to the other side of the rectifier from the W/G connection.

Joined: Sep 2013
Posts: 3,440
Likes: 156
Q
Britbike forum member
Online Happy
Britbike forum member
Q
Joined: Sep 2013
Posts: 3,440
Likes: 156
Originally Posted by koan58
If you have a decent ohm meter, test resistance between each pair.

One pair will have the highest reading. Mark the other wire White/Green.

Now test the 2 wires against that W/G.

One will be lower resistance, that will be G/B

The higher resistance to G/W will be G/Y.

The understanding of this is that the G/W is common to all the stator coils, and should be a sole connection to one side of the rectifier.

The G/Y is from 2 pairs of coils (high output)
The G/B is from 1 pair of coils (low output)
Any routes of these must go to the other side of the rectifier from the W/G connection.

You're going to need better than home shop equipment
to measure ohms below 1 .

The test probes and how hard you press them and if your finger flesh is on a probe
will all throw the readings off .

Joined: Nov 2012
Posts: 2,283
Likes: 104
K
Britbike forum member
Offline
Britbike forum member
K
Joined: Nov 2012
Posts: 2,283
Likes: 104
Hi Quinten,
I did preface with:
"If you have a decent ohm meter, test resistance between each pair."

My meter easily distinguishes between 0.1 to 0.5 to 1.0 ohm, which is what is necessary here.

If the PO's meter is up to it, my instructions will be valid.

Joined: Feb 2019
Posts: 715
Likes: 248
S
Britbike forum member
Offline
Britbike forum member
S
Joined: Feb 2019
Posts: 715
Likes: 248
Originally Posted by koan58
One will be lower resistance, that will be G/B

The higher resistance to G/W will be G/Y.

The G/Y is from 2 pairs of coils (high output)

The G/B is from 1 pair of coils (low output)
Two pairs of 140 turn coils in parallel (high output) feed the G/Y wire and it will actually show the lower resistance. I only mention this in case the bike uses switched regulation. Otherwise, it won't matter.

If the 4 high output coils were all in series, THEN the G/Y wire resistance would be higher than the G/B wire.

Joined: Oct 2003
Posts: 4,194
Likes: 14
D
Britbike forum member
Offline
Britbike forum member
D
Joined: Oct 2003
Posts: 4,194
Likes: 14
Maybe Pete could take the stator to an electronics firm to have the resistance tested on a posh meter.

Dave

Joined: Aug 2001
Posts: 8,809
Likes: 101
T
Britbike forum member
Offline
Britbike forum member
T
Joined: Aug 2001
Posts: 8,809
Likes: 101
I’d do it by output, judging the brightness of a headlight bulb.

Find the brightest combination and connect that to a 12V regulator.

You guys are right though, the open coil stator is likely to fail from vibration damage before too long.


Amateur Loctite enthusiast.
Joined: Aug 2021
Posts: 2
S
Novice poster
OP Offline
Novice poster
S
Joined: Aug 2021
Posts: 2
Thanks to everyone for the replies. Apologies for not replying sooner but as any retired person knows, you never have any spare time to get round to doing the important things in life.
So much valuable information :- I'm genuinely impressed.
I do have a decent digital multimeter so I hope to be able to get some decent results. I intend to do some initial resistance testing and hope to identify the individual wires from that. Whether I do or not, I'll still run the bike on battery and check outgoing voltages, and I'm sure, with all the information you've all given me I'll solve the problem.
The bike is running a 12 volt system at present with Lucas RM.19 alternator and Zener diode.

Steve, I appreciate your recommendation to replace the old stator with a new resin encapsulated one. I know it makes sense, but stator and coils look to be in such good condition I feel I should try to get it running. (These words of mine are just a cover up. Ask any Brit, we Yorkshire men will go to the ends of the earth to avoid spending money.)
Thanks again everyone. Alll advice is much appreciated.
So glad I joined this forum.

SmallpersonPete


Moderated by  John Healy 

Link Copied to Clipboard
Job CycleBritish Cycle SupplyMorries PlaceKlempf British PartsPodtronicVintage MagazineBSA Unit SinglesBritBike SponsorBritish Tools & FastenersBritBike SponsorBritBike Sponsor






© 1996-2021 britbike.com
Powered by UBB.threads™ PHP Forum Software 7.7.5