Wiring in General
I prefer to use "marine-grade" wire wherever I can on the motorcycle. Marine grade wire has several desirable properties for moto use. It is 'plated' wire - meaning before it becomes wire, the individual strands are tin-plated. This plating provides excellent resistance to corrosion. Wire will corrode if exposed to a wet/damp atmosphere due to 'wicking' of water up the wire strands. Since I live less than a mile from the Atlantic Ocean, this is can be a concern. The other plus for marine grade wire is that it usually is made of finely stranded copper - allowing for better flexibility and resistance to vibration induced fatigue failure. The tin plating also makes soldering the wires easier.
It is not a requirement that anyone use marine grade wire, but if you can find it (in most large boating supply stores) it is a better choice for motorcycle wiring.
Soldering vs Crimped connections
Each has their proponents - and each has places where it is better, but in general, I greatly prefer good soldered connections for motorcycle use.
Soldered connections are inherently resistant to failure caused by an improper crimp. Why do bike/auto manufacturers use crimped connections? Cost. It's cheaper to crimp than solder - due to the time required to do a good solder connection. A *good* crimp connection can be done with the $5.95 tool found in the home-handyman store, but repeatable GOOD crimps are done by wiring harness manufacturers using tools which cost $100 or more, which are sized for one size crimp connection, and are frequently compound lever action tools designed to put an optimal force on the crimp and then release - avoiding undercrimped or overcrimped (crushed wire strands) connections.
In this project - all connections were soldered and in addition - protected via the use of "shrink-fit" tubing which tends to provide mechanical reinforcement and some weather sealing. The use of shrink-fit for crimped connections is also an excellent idea for the same reasons.
A FWIW - I have been soldering electronic components for something close to 5 decades, so my personal preferences may have some influence on my decision to use soldered connections. An additional FWIW - in the past 40 years I have not had a failure of a single joint that I've soldered, I have had failures of crimped connections.
Mounting the relay
As can be seen in the pictures on the previous pages, I used "spiral wrap" to make two lead assemblies which have the male/female plugs at each end (shown on Assembly Photo (Page 3). The wires on the plugs were the length needed for my planned mounting position, so no splicing in of additional wire was needed. Spiral wrap was found in the same auto-parts rotating bin that I found the headlight plugs in.
Mounted in the bike, the entire assembly mounts to the fairing screw directly behind the right side glovebox. This makes it easily accessible, yet keeps it out of any weather. When the glovebox is reinstalled, it is not visible, nor is there any danger of shorts to the relay contacts.
The two lead assemblies with the male/female connectors on them were routed along the front of the upper fairing mounting bar (a large L shaped metal piece going from the outer fairing mount to the mounting on the frame). They are tie-wrapped in position. The stock headlight plug was removed from the headlight bulb and the home-made male connection was plugged into it. I 'tied' the two together with a small tie-wrap run around both of them. The new female socket was plugged into the bulb.
As I mentioned - I wanted easy reversibility - which only requires snipping the tie-wrap, unplugging the plugs and returning the stock female plug to the headlight bulb. Haven't had to do this - but I like things that can be easily undone.
Powering the Relay
I powered the main feed for the relay assembly off the bike battery. There are other options, such as powering it off the 'unloader' relay in the fuse box. The primary reason I used the battery for a power feed is it let me put the fuse where it's handy, and I'm lazy and didn't feel like taking the fuel tank off to get into the electrical box. The choice is yours.. Brian Curry's FAQ on headlight relays describes getting a feed from the electronics box. Sometime in the future I may use Brian's technique!
The main power feed for the relay assembly is a number 12 marine grade (tinned) wire - encased in 1/4" OD Teflon tubing, which protects the wire from any possible abrasion wearing through the insulation. I routed it up the right side of the bike, tie-wrapped it along the frame, and under a filler plastic piece between the tank and fairing. It ended up being well protected from abrasion and the elements.
I used a mini-spade fuse assembly, with a 30 amp fuse, directly connected to the battery to power this wire. These are also available at auto-supply shops (usually in the same rotating rack as the other components), and have the advantage of being totally weather-tight and using readily available fuses.
CAVEATS - DISCLAIMERS!
This FAQ describes what *I* did on my K bike. I take responsibility for MY safety seriously, and I am happy with the results of this modification to the bike.
I do not recommend that you do this modification, nor would I take any responsibility if you ignore this advice and do it, and it fails causing you to crash and kill yourself. If you are of a litigious nature - please leave your bike as BMW intended.
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