Wire Gauges

[whiskey pete]

Was replacing some questionable wire segments and realized that I used a smaller gauge wire in the splice. Not by much but still smaller. Conventional wisedom says to always wse the same gauge but I was wondering if there was any slack allowed or if some systems are more gauge critical than others. I tried a search under several keywords and nerver really found a "rule of thumb" sort of speak. By the way HNY to everybody.

[jetmechmarty]

Using smaller gauge wire in a circuit is not a good idea. The wiring was engineered for the current it has to carry. The fuses are installed to protect that wiring. You may be OK, but I recommend doing it over with the proper gauge wire.

[crazy steve]

Was replacing some questionable wire segments and realized that I used a smaller gauge wire in the splice. Not by much but still smaller. Conventional wisdom says to always use the same gauge but I was wondering if there was any slack allowed or if some systems are more gauge critical than others. I tried a search under several keywords and never really found a "rule of thumb" sort of speak. By the way HNY to everybody.

Vehicle manufacturers are notorious for only using 'adequate' sized wire in harnesses (sometimes barely adequate), so going undersized is never a good idea. This can also cause additional voltage drop, something that plagues these bikes anyway. If it's in an 'intermittant' circuit (like the turn signals, brake light, or horn), you'll be less likey to have problems, but it will still be a potential trouble spot...

[whiskey pete]

I guess I need to tear that stuffout and rework. I also noticed that some of the wires are steel instead of copper. Can I mix or same rule applies? Thanks Guys............

[crazy steve]

None of the wires are steel, but some are tinned copper. Mixing is no problem...

[Danny Crawdad]

My rule of thumb on stuff like that is that it may pass without a problem, but if I'd be cussing at a previous owner for doing it, I try not to myself

[Laptop_geek]

There are so many variables when choosing wire sizes it can not be answered simply. As a general rule, you should always use the same size or larger wire, but in some cases smaller will work fine. Wire basically acts as a very small resistor, and as such it heats up whenever current is passed through. The larger the wire the less resistance, the smaller the wire the more the resistance, and therefore more heat. The insulation must be able to withstand this heat. If it does not you will "fry the wiring". Insulation must also keep the wiring from shorting or grounding itself. Insulation also helps to dissipate heat by allowing a greater surface area for natural convection. These are the main purposes the insulation on a wire serves.

Here are some questions that need to be asked:

First; what parts of the harness were you repairing? If it is something that will not be negatively affected by a small voltage drop it may actually work out fine.

Second; what type wire did you use to replace it with. Was it aluminum or copper? Aluminum has a higher resistance and it will have to be a larger size, the opposite is true for copper.

Third; What was the type of insulation on the wire you used when you did the repairs? Different insulation will with stand different amounts of heat.

Fourth; What is the original size of wire and what is the size you used in the repair? It was mentioned that manufacture like to skimp on wire sizes, this is due to the high cost of material for wire (mostly copper) and the high weight of material. If they are able to get by with a size smaller they will, it will save them manufacturing cost (maximizing profits) and it will increase fuel mileage, handling, and performance. Figuring all this out is what the engineers are busy doing all day long.

I'm sure there are other factors, but I think this covers the most of them.

[XS1100_OEM4ME]

Jmho

JMHO, you don't want to hope it is OK, so now is the time to be sure "IT" is not the problem when something acts up later. 2nd, in addintion to different kinds of wire (alum copper nicrhome, etc) there is a big disserance in auto and motorcycle wire. Auto wire is not made to handle the constent flexing that motorcycle wire has to take. This is most important in the wires that go from the frame to the triple tree, as they flex constently. The are made of much finer braids of many small wires made of more flexable componds. The cheap auto store stuff may be of the same gauge but will break with the flexing involved with turrining the front wheel left and right over and over. This is why the cheaper alum wire is never used in these connections, higher tin content can lead to the same thing. So, on the frame points where no, or little flexing will happen, the same or higher gauge copper base wire is fine. In the wires that run from the frame to the front wheel or any other place where constent flexing will happen, us only motorcycle type fine weave wire of the same gauge as stock, not steel, nichrome or high tin. It may last for a while or it may break with time, why take a chance

[XS1100_OEM4ME]

High flex wire

This site tells more about high flex wire and its use:

http://www.calmont.com/flexible-wire-cable.php

[XS1100_OEM4ME]

Steel wire

And yes wire does come in steel, as well as brass and many other componds. The steel it used for keeper wire for the most part, and SS wire the same, but in high exposure areas
http://www.malinco.com/

[XS1100_OEM4ME]

Helpful

I want to be truly helpful to you, and understanding fixing the wires on a 30+ year old bike can be dauting. 1st, Yamaha used three "kinds" of wire on these bikes for cost and relieabilty concerns. The main harnes is cheap standard copper wire of a gauge just adequate for the needs (ie, you can replace any of these with cheap auto store wire of the same or larger gauge wire) 2nd, you will see the the wires that go from frame to triple tree are the type I mentioned, fine thread high flex componds, most plug into the main cheap wire harnes with a milti plug connector. All of these need to be the high quilty flex wires, along with most of the lighting wires, like the ones inside the headlight, due to vibration (that is why they feel so flexable compaired to auto wire) 3rd is the low amp extreamly flexable wire used in places like the ign advance to the pick up coils, many break from flexing as the wire tech of the day wasent up to that much flexing. You will see how many members have fixed the break, but that just moves the high flex point to a different part of the wire, and will break again, most likely. If you use the right wire at the right places, you will be set for a very long time, good luck with your bike

[whiskey pete]

I always told my kids that there is only one way to do something...That is correctly. I replaced some sections that were worn through or excessivly kinked. I used sections from another Yamaha harness. The problem came when I tried to stay consistant with the color code. Almost all the color combinations came in different size wires depending where on the harness I took the wire. Thanks for the help guys.

[crazy steve]

Lon, both you and Geek are confusing the issue, and some of the things you're saying aren't true...

Wire size is selected for it's amperage-carrying capabilties, period. Now, there's all sorts of factors that can effect the size calculation (almost always reducing it's rating), but unless you're trying to skimp as much as possible you can usually disregard them. One big problem with automotive/vehicle wiring is there isn't any clear-cut guidelines for selecting wire sizes, with nearly every 'guide' you find reflecting that persons' idea' and few of them agreeing. If you're looking for a dead-nuts 'safe' rating, use the NEC numbers: #18 - 5 amps, #16 - 10 amps, #14 - 15 amps, #12 - 20 amps, and #10 - 30 amps. Automotive designers will increase these numbers generally about 30%, and you would be safe doing so in most cases.

Wire resistance isn't a factor in a properly-sized wire; keep in mind that the ohm difference between a #18 wire and a #12 is smaller that we can measure with the meters availiable to a home mechanic; you're talking about .006 ohm per foot for 18, and .001 per foot for #12. On a 2 amp circuit, the 18 will drop .012 v per foot, and the 12 will drop .001 v; a difference of about one-hundredth of a volt. Where you'll get into trouble is if you put too much current in the circuit; exceed the amps rating, and the wire will start to heat up. More heat, the resistance goes up, bigger voltage drop. A example of this at work is any light bulb; measure resistance through a turn-signal filament and you'll get about 2.1 ohms 'cold'. Apply power, and it jumps to 6.1 ohms, or almost triple.

Wire insulation is a non-factor in figuring wire size for a vehicle also. Your basic thermoplastic insulation is nearly always good for 60 degrees C (about 140 F), and you shouldn't be seeing temps that high except in certain places. On the XS, they did use a higher-temp-rated insulation on the leads out of the alternator, but that has much more to do with high ambient temps (being in close proximity to the motor) rather than a need due to heat generated by current. At the first plug into the rest of the harness, they switched this to 'normal' plastic wire. And any insulation reduces ampacity; compare a bare conductor in free air vs an insulated one; the bare will be rated higher. Now, somebody is going to say 'if insulation doesn't matter, why is there different ratings and higher-rated insulations are good for more amps?' Well, those higher amp ratings are there for the engineers to use in 'special' applications. The higher temp ratings are so you can select a wire that will withstand the ambient temps the wire will see. One thing seldom mentioned is the fact that nearly all commercially-available connector/terminations (plug connections, splices) are only rated to 60 degrees C, and all ampacity calculations are supposed to be done to the lowest-rated part of the circuit. Ignore this at your own peril..

This last item brings up de-rating factors. There's almost more of these than you can count, but the short answer is ampacity ratings will be affected by ambient temps (colder more amps, higher less), and is the wire in free air by itself (the highest rating), enclosed in something or 'bundled' (all reductions). You can pretty much ignore the 'multiple conductor' derate as you've only got a few circuits that operate full-time on a bike (lights, ignition, charging system), but you will have a small reduction simply if the wires are in a wrapped harness.

Wire 'flexability'.... Sorry Lon, but the XS uses the same wire type throughout the whole harness except for the mentioned alternator leads and the short pieces to the pick-up coils. I'll agree that the usual parts-house 'automotive' wire is a poor replacement for any factory wire, particularly across any point where it has to flex, but if you're using where it won't be moving it's acceptable. Aluminum wire is another non-issue, as you can't even buy it in sizes smaller than #6 anymore, and it should never be used in a automotive application.

I use THHN or THWN stranded building wire sometimes and have had good luck with that, but the difficulty is finding it in the small amounts we need and a limited color selection. Being a retired electrician, I saved 'scraps' for years, so I've got boxes full of odd pieces that I'll dig through when I need a short bit, but I prefer to use OEM-type wire. I have used that 'Superflex' wire and it's great stuff, but the cost!!!??? I recall buying some in a large size and it was over $70 per foot!

Bottom line? Never replace with anything smaller, go up one size if in doubt, and if you like to solder, use strain relief (I almost never solder vehicle connections...).

[crazy steve]

..The problem came when I tried to stay consistant with the color code. Almost all the color combinations came in different size wires depending where on the harness I took the wire..

Pete, these guys (http://riwire.com/) are the best I've found in being able to supply small amounts of automotive-type wire with the right color codes for reasonable prices...

[XS1100_OEM4ME]

Resurch

After doing more resurch, I found this to help simlify my point of view It starts to make more sense about halfway through
http://www.youtube.com/watch?v=Rd5k7J7bIOk