Aftermarket Speedo (Turn Signal Indicator)

[spayne83]

I am hooking up an aftermarket speedo and I have everything sorted (with the exception of the gearing, but oh well) but I am running into a problem. The speedo only has one light for the turn signal indicators and on my wiring diagram there are two lights on the stock unit.

The speedo light has a power and ground so I was thinking that I can splice the power wires from both turn signals together and place one "downstream" of a diode so that it doesn't power both signals at the same time, but it lights the indicator.

Will this work? What size diode would I need?

[DGXSER]

To be clear how I would suggest this, I would install a diode in the brown and dark green wires that were feeding the turn signal indicator lights, as close to those lights as possible, meaning down stream of any splices to feed the turn signals.

That way the diode only sees the current flow in either direction of the turn signal indicator lamp in your new setup. Both circuits are protected, both circuits can light the indicator lamp. So each diode would need to be rated for say 16V as your system voltage could get that high, and I would select the diode at say 130-140% of the rated amps for your indicator bulb, which is probably next to nothing if it is an LED.

[crazy steve]

Depends on what type of indicator light is in the speedo; if it's a LED, you'll need a diode in each power wire from the signals before tying them to the power wire to the light. Size doesn't have to be big as this is a very low current circuit, just make sure it's rated for at least 15 volts.

If it's an incandescent lamp, simply hook one wire to one turn and the other to the other turn; no diodes needed. This is assuming you're not using LED turns; if the turns are LED, see above. This is what Yamaha did on the SF bikes....

I'm curious; what speedo are you using? Does it have the right ratio?

[spayne83]

Here is the current iteration of my wiring diagram:



I have the diodes installed right before the connector to the one turn signal light. I think that that is correct.

[DGXSER]

That is how I would wire up the turn signal indicator.

[spayne83]

Thanks for the help.

I going to go with the flexible LED lights (http://www.radiantz.com/index1.html?250.html&1) so I think a 16 VDC 2A diode would be ok.

I speedo came with the bike and doesn't have a brand on it, so I'm not sure, but at least it gives me a general idea of how fast I'm going. I'm going to try to get an aftermarket Tach to match up with the stock tach (or at least close) so that I can have a better idea of the actual speed. 3000 @ 65 in 5th is always the same.

[TopCatGr58]

Thanks for the help.
I'm going to try to get an aftermarket Tach to match up with the stock tach (or at least close) so that I can have a better idea of the actual speed. 3000 @ 65 in 5th is always the same.

Hey Spayne,

Our tachs do not work on the ignition system, they work off of one of the 3 legs of the alternator, and I don't think any other aftermarket tachs will do that. They usually get a trigger signal from the (-) terminal of one of the spark plug coils. And IIRC it will need to be set for a 2 cylinder mode.

T.C.

[spayne83]

Thanks for posting that. I had read a few places that that was the case, so I am going to try it and report back so that we can confirm whether or not that will work.

Here is a picture of the speedo



And the back



So I'm pretty sure that the ratio is a little low so that means that the speedo will read high (if I'm doing the math right) and will keep me from getting speeding tickets!

[Eveready1100]

A little low? It's about 1/3rd out. You want to watch you don't get run up the rear on the freeway with that one.

[mmaddix]

I have that same Speedo but with a white face and I was running led turn signals so I put one of these diodes http://www.amazon.com/gp/aw/d/B000TK7XMY

Here is a diagram to install http://www.customdynamics.com/load_equalizer_diodes.htm

Also my Speedo was on the bike when I got it and it it pretty accurate. Maybe the guy that had it before already modified it for the correct ratio.

[crazy steve]

...Also my Speedo was on the bike when I got it and it it pretty accurate. Maybe the guy that had it before already modified it for the correct ratio.

At one time these were available with the right ratio for the XS, but the supply seems to have dried up...

I've got the same speedo on my chopped '86 Sportster, but it's right for that speedo drive.