1974jh5
Curmudgeon.
osteoderm's excellent build thread got me to thinking. The number one problem with old bikes and cars is the electrical stuff is worn and corroded. That means people will patch the harness to keep the bike or car going, that's fine but if not done properly will cause more trouble than the original failure. Sometimes it's necessary to build from scratch, so after building and repairing many harnesses I'm going to lay out what I have learned the hard way, often via the 'let the smoke out' method.
Take a few minutes to really think through how the wires will route, consider things like needing to replace or access something quickly. Will you be using stock components that you may need to replace later (rectifier, ignition switch, etc)?
Also consider (as Yamaha did) running multiple circuits on a single fuse to cut down on the size of the fuse block. I will say that Yamaha did cut some corners, I think these bikes need six fuses instead of four, as in: headlights, brake/tail lights, charging system, ignition system, horn and turn signals. Horns (particularly loud ones) draw a LOT of power, BTW. Yamaha put the horn, brake lights and turn signals all on the same circuit. That means if the horn pops the fuse you also lose the brake lights! Not good.
When choosing connectors for building race car harnesses, I prefer the Weatherpak connectors.They are well engineered and sealed against water intrusion and thus corrosion. Weatherpaks:
Unfortunately, IMHO Weatherpaks are too big and bulky for bike use. The molded nylon OE connectors that Mike's sells are decent stuff from an amp draw and voltage drop standpoint, but still a bit bulky.
Yamaha used them because they are cheap. Sometimes you may need to use them, such as where the stock ignition switch plugs into the harness. If you don't use an OE connector on the harness, you will have to cut/splice/etc if you buy a new OE part. They are also not weather sealed.
The 'bullet' connectors with the silicone sleeves sold by Mike's are very good stuff. We used to use those on RC cars, the voltage drop was surprisingly low and in one test it took ~120 amps at 7.2 volts to cause a failure. Your fuse should blow first! The silicone sleeves are very good at sealing water out.
The winnar for availability and size are those white plastic connectors available at Radio Shack, they are known as Molex connectors. The amp capacity and voltage drop will be sufficient for pretty much anything on these bikes and they are pretty small.
They are not waterproof, though. When you wash your bike, even the mildest soaps are sort of caustic and will start corrosion. So if you use those connectors, pack the back side with clear silicone sealant. After that dries, use a dab of dielectric grease when you put it together for years of trouble free operation. If you use the OE type connectors, treat them the same way.
If you decide to build your own harness and you don't know how to solder, learn this skill first. Practice on scrap wire etc, learn how to make a good solid soldered connection. Then smear a little dielectric grease on the solder joint and slip some shrink wrap over it for a long lasting waterproof connection. About solder joints: they should always be in a straight and well supported run of wiring, not in a turn or where the joint will flex a lot because that will lead to early failure.
If I catch any of you using Scotchloks I will YELL AT YOU IN CAPS TILL YOU DIE. Please forget those things exist. This is a Scotchlok:
They slice through the insulation and cannot be sealed well, meaning corrosion. They also 'guillotine' the wire, causing strands to break inside the insulation. I will use them only in a dire emergency to get me home where I can make a proper repair.
While on this subject, these sold at the auto parts store and the big box hardware stores are garbage as well:
They are corrosion prone and the female side has very little 'spring' to it, meaning they do not grip the male part well. Also, that big plastic 'barrel' does not support the wire, making it easy for the wire to flex and break right at the connector.
Take a few minutes to really think through how the wires will route, consider things like needing to replace or access something quickly. Will you be using stock components that you may need to replace later (rectifier, ignition switch, etc)?
Also consider (as Yamaha did) running multiple circuits on a single fuse to cut down on the size of the fuse block. I will say that Yamaha did cut some corners, I think these bikes need six fuses instead of four, as in: headlights, brake/tail lights, charging system, ignition system, horn and turn signals. Horns (particularly loud ones) draw a LOT of power, BTW. Yamaha put the horn, brake lights and turn signals all on the same circuit. That means if the horn pops the fuse you also lose the brake lights! Not good.
When choosing connectors for building race car harnesses, I prefer the Weatherpak connectors.They are well engineered and sealed against water intrusion and thus corrosion. Weatherpaks:
Unfortunately, IMHO Weatherpaks are too big and bulky for bike use. The molded nylon OE connectors that Mike's sells are decent stuff from an amp draw and voltage drop standpoint, but still a bit bulky.
Yamaha used them because they are cheap. Sometimes you may need to use them, such as where the stock ignition switch plugs into the harness. If you don't use an OE connector on the harness, you will have to cut/splice/etc if you buy a new OE part. They are also not weather sealed.
The 'bullet' connectors with the silicone sleeves sold by Mike's are very good stuff. We used to use those on RC cars, the voltage drop was surprisingly low and in one test it took ~120 amps at 7.2 volts to cause a failure. Your fuse should blow first! The silicone sleeves are very good at sealing water out.
The winnar for availability and size are those white plastic connectors available at Radio Shack, they are known as Molex connectors. The amp capacity and voltage drop will be sufficient for pretty much anything on these bikes and they are pretty small.
They are not waterproof, though. When you wash your bike, even the mildest soaps are sort of caustic and will start corrosion. So if you use those connectors, pack the back side with clear silicone sealant. After that dries, use a dab of dielectric grease when you put it together for years of trouble free operation. If you use the OE type connectors, treat them the same way.
If you decide to build your own harness and you don't know how to solder, learn this skill first. Practice on scrap wire etc, learn how to make a good solid soldered connection. Then smear a little dielectric grease on the solder joint and slip some shrink wrap over it for a long lasting waterproof connection. About solder joints: they should always be in a straight and well supported run of wiring, not in a turn or where the joint will flex a lot because that will lead to early failure.
If I catch any of you using Scotchloks I will YELL AT YOU IN CAPS TILL YOU DIE. Please forget those things exist. This is a Scotchlok:
They slice through the insulation and cannot be sealed well, meaning corrosion. They also 'guillotine' the wire, causing strands to break inside the insulation. I will use them only in a dire emergency to get me home where I can make a proper repair.
While on this subject, these sold at the auto parts store and the big box hardware stores are garbage as well:
They are corrosion prone and the female side has very little 'spring' to it, meaning they do not grip the male part well. Also, that big plastic 'barrel' does not support the wire, making it easy for the wire to flex and break right at the connector.