Hi Andy,
cables are generally 28/0.30?
If what's on the bike now is original, all wires in
all original '71-on looms were/are 14-strand, including all the Red wires and the Brown/Blue.
Moreover, original strands are slightly smaller (32SWG) than modern metric (0.3 mm.), so Lucas rated original wire for only 7.5A ... exceeded by the standard alternator above about 2,000 rpm. :Not again It's one of the "cheap shortcuts" I've posted about before, even modern 14/0.30 is only rated for 8.75A, all modern off-the-shelf looms copy original Lucas in this respect so it's one reason I don't use modern off-the-shelf looms.
Suggestions:-
. The standard Lucas (original Lucas) implementation of Red return wires is over-complicated and fails if more than one wire breaks ... :Not again
. I use two of
these, one in the headlamp shell and the other under the seat. Each individual component Red wire is connected to the nearest, they're connected together with two lengths of 28/0.30 'thinwall' (higher-rated but thinner overall than standard PVC-insulated) that join attached to an engine head-steady bolt/stud. On a pre-'79 kickstart-only bike, this simplified network is joined to battery +ve by a 28/0.30 Red wire from the underseat "Sleeve Connector", through the main fuse/holder.
. In addition to the aforementioned Red wires, I also use 28/0.30 thinwall for the Brown/Blue wire and the White wire between the ignition switch and Sleeve Connector in the headlamp shell that's the junction of individual component White wires.
. I fit relays in the headlamp supply as a matter of course, even if the existing headlamp is the crap standard BPF; if you don't fit relays, I advise 28/0.30 thinwall also for the Brown/White between Ignition Switch and Lighting Switch (on a '73).
. Apart from those wires, all other wires are to/from individual components could be 9/0.30 as its 5.75A rating isn't exceeded by the consumption of any component, the only thing that precludes this is not all colour combos. are available in 9/0.30.
. I use the above wire sizes plus 14/0.30 because crimp-on bullet terminals that work are available for all three from both Autosparks and VWP. The "1 sq.mm." (aka 14/0.30) ones don't work reliably on original Lucas wire (e.g. switch cluster wires, because of the aforementioned smaller strand diameter); for those, I have/keep some
http://www.vehicle-wiring-products.eu/product.php/453/w-crimp-type-4-7mm-bullet.
. When ordering from VWP, they also sell a variety of button contact that can, if necessary, be used in the insulated part of bulb holders (couldn't find the link
).
. Red wire from the B-B "Transistor Box" connected directly to battery +ve terminal.
. Red wire from coils' series connected either directly to battery +ve terminal or underseat Red wires' Sleeve Connector.
. Fuse in either the Transistor Box White wire (preferably) or Red wire.
. Connect its DC wires (Red and Black?) directly to the corresponding battery terminals, one or other through a fuse (not the main fuse protecting the loom); don't replicate the standard Lucas rectifier connection in the Brown/Blue wire to connect the reg./rec.
. Bear in mind wrapping was/is only to keep a manufactured loom together during transport (and original fitting on the bike-building production line). Once a loom's on the bike, any wrapping's just a pita.
. I've never wrapped any loom I've built. On a bike, I start by securing wires to top frame tube and drive-side seat tube (on a 'dry-frame' keeps the wires away from possible oil contamination) with releasable reusable cable ties. My first loom, having built it, I just couldn't be arsed to take it apart to wrap it. Turned out to be an inspired choice because I still own the bike, it's had some upgrades over the years, :whistle which were wa-aa-ay easier than if the loom had been wrapped.
. Any loom I build, once it's complete, tested and mostly covered by tank, seat and sidepanels, any wires still exposed I cover with lengths of what Autosparks calls
Split Convoluted Conduit (scroll down the page to see the different sizes) and VWP calls
Slit Convoluted Tubing ("Slit" is in the "Options:" drop-down); the Split/Slit is lengthways so the Conduit/Tubing can be fitted or removed from wires without needing to disconnect and thread them. :thumb
. If the headlamp shell has three wiring holes, I always split the wires to/from the frame and thread them through the left and right shell holes (and OIF frame gusset holes?). To allow Conduit/Tubing beside other wires or cables, Autosparks sell a
grommet with a larger centre hole, or you can simply cut out standard grommet centres?
There seem to be redundant wires that I think shouldn't be redundant,
Off the top of my head:-
. Twins with points originally had a supply wire (White/Yellow on your bike) to each coil "-" terminal; only one's required for the B-B Transistor Box White wire so the other White/Yellow is redundant.
. Points require condensers, their connection was (on your bike) one of the two Black/White and Black/Yellow wires originally attached to each coil "+" terminal. The other Black/White and Black/Yellow wires originally to the points are now being used between the Transistor Box and the (B-B) "Stator"? So the condensers and wires to them are redundant.
. If the reg/rec. DC- (Black?) wire was connected to the original Brown/Blue wire rectifier connection, as I say, imho both reg./rec. DC wires should be connected directly to the corresponding battery terminals, so any break in the new Brown/Blue wire isn't required. :thumb
. Similarly, with any reg./rec., the original Brown/Blue connection to the Zener is redundant, as is the Red wire (usually) attached to your bike's airbox between the original rectifier and Zener mountings.
recently re-wired a 72 T100R, using a new 'Lucas' loom
interesting that yours is taped. Looking at pattern looms they are all fabric covered.
It's one of the changes Wassell ("Genuine :rofl Lucas") make to suit themselves; ime, Autosparks and British Wiring looms are wrapped correctly for their application; afaict, all 'original Lucas' looms were taped '71-on; however, it's becoming harder to be sure because even replacement looms can be old and tatty.
As Don posted, taping the wires between frame and headlamp shell is a crap idea; on my first T160, the White/Yellow wire broke there within a couple of years, because the wires had been taped too tightly by whoever built it at Lucas.
arn Simply covering them with tubing, wires can move and flex individually as required when the forks are turned.
sleeving
to
points chest.
If your bike still has the original points cable, with the Black/White and Black/Yellow wires encased in black insulation, bear in mind the rubber seals in crankcase and timing cover were intended to work with that. Otoh, if you fit the seals over sleeving, it folds between the seal ID and over the wires inside, allowing a space for water to enter.
If you don't have/use an original points cable, Autosparks has the larger selection of sleeving OD; use the one that completely fills the passage through the crankcase and timing cover and leave out rubber seals.
Hth.
Regards,