Finally took the whole headlight assembly and started the work. Will do it the tried and tested way of fitting dual relay kit and a better H4 bulb.
Picture shows the plug & play kit from Easternbeaver and Osram Nightbreaker bulb.
All this should fit inside the headlight unit.
Notice also the proper thickness of wiring from relays straight to battery posts, via fuses on both wires naturally. Should keep the voltage loss to minimum.

Also wanted to see how difficult ( or easy ) it is to attach pictures here.
Not too difficult, as even I could do it...

 

And as I predicted the headlight is simply too small to fit the 2 relays and additional wiring inside.
So some wiring work is needed too. I was so much hoping it would be simple plug and play, but now some modifications are needed. And leaving the relays out from headlight itself. Shouldn´t be too hard though, as the relays are smallish and if I recall correctly can handle some water/moisture/humidity.
The good thing is, I checked the relay wiring and it is AWG14, and when I compared to the original wiring for headlight, the original is really thin. Like half of the AWG14 wiring.

 

I'll be following this thread as I'm considering the same relay for the headlights/spots on my Road King. Good luck and post up some pictures....

 

Took a bit longer than I planned to do this.....
Was a bit frustrated that the doublerelays & double H4 connectors & some wiring simply doesn't fit inside the headlamp.
Dismantled carefully the new H4 connector, thus I was able to squeeze the new thicker wires through the hole I drilled for the wires, one wire at a time. Then put the connector back together and all is now ready.
All I have to do now, is to connect the original (cut) headlamp wires to this kit. The kit has a female H4 socket for the connection, but I will cut it out too.
The small relays will be left hanging there, under or behind the headlamp, the wires are simply too short to move it far. Should be able to find a place to attach those.
Then I will connect those together leaving the 2 bulky H4 connectors out. Will be using the Posi-Lock connectors, just because they are easy and should work nicely there. And the original headlamp wiring that I cut and later will connect to the relay wiring will only supply the signal to relays from switch. The thicker new wiring I did not cut, wanted to keep it in good order, no added cuts or connectors on that. Should get all the voltage available to the new bulb, without any losses.
Naturally also need to get the new thicker wiring connected to batteryposts.
Will take pics and write some info when I get it mounted back to the bike.
The results in added output through relays, proper wiring from battery to bulb and a better bulb should be clearly visible. We'll soon know...
A thing worth considering with Sportsters is, as there is no room for the relays inside the headlamp anyway, is to mount the relays under the seat/next to battery. But that would mean more wiring work, which I didn't want to do. Mainly because I purchased this ready made kit just to avoid all wiring work and make the installation easy and fast...

 

What is the intended outcome for this relay? brighter lights?

 

Yes, the known fact is that the stock wiring through switch, without relays looses voltage. With the relays and proper thickness wiring the voltage loss is minimized. And the added good bulb should give out visible difference, without anything being visible. Or illegal.

http://www.danielsternlighting.com/t...ys/relays.html

I did some calculations using a wire loss calculator and the before mentioned DS Lighting chart too:

If the voltage is 12.8volts, and the load of headlamp is about 6 Amps, the lenght of wiring is 20 ft, using the relay kit and thicker AWG14 wire in it, I should get 12,49 volts to the bulb. If the bulb gives out 1000 lumens at 12.8 volts, I should get out 923 lumens.
If the voltage is the same, load is same, length of wiring is the same, the original wiring which I think is AWG18, the voltage at the bulb is about 12 volts.Output of the same bulb dropped to 803 lumens.
If all stays the same, and the wiring is AWG20, the result is shocking 11,5 volts at the bulb and only 700 lumens.
I simply can´t be sure what the original wiring is, it seems to me it is either AWG 18 or AWG 20.
Of course it is never as simple as this, many things affect the result. Just wanted to experiment and educate myself.

 

I have completely forgotten to upgrade here, sorry.
All wiring finished, relays mounted, and it works flawlessly.
And the light is now bright, really bright. Naturally can't say how much brighter as I have no way of comparing it to the original one. And I also replaced the bulb with a better one.
Highly recommend this upgrade for anyone who want's to stay with common H4 bulbs.
The only thing I don't like with this is the fact that the ready made kit I used, doesn't fit inside the headlight. There simply is no room.
This means I had to leave the relays outside headlight, they are now attached under the headlight.
If I would do this again, I would build it myself, using relays mounted under the seat or something like that. And mounting, cutting and soldering all wires myself to make it look nice and all wire lenghts would be custom made and right length.
There is nothing wrong with this kit, it is SO nicely done. And the relays are ultra small etc. I just originally didn't want them to hang outside, now getting wet in the rain etc, but the kit and length of wires prevented mounting them further from headlight.

 

I was thinking of doing this to my Fatboy...I should be able to fit everything in the 7" headlight. This is a common upgrade on older jeeps too.

Where did you get the prewired kit? I have some 8 an 10 ga wire left over an was going to run a lead off the battery. I could just buy 2 30 amp relays but will look at the kit if it isn't too much so I know the connections are solid.

 

I ordered my kit from these guys :

http://www.easternbeaver.com/Main/Wi...s/h4_kits.html

A superb kit, highly recommended ! I can do basic wiring, soldering and shrink tubing myself, and still think it was worth the money spent. I simply didn't have the time or place for a DIY job this time.
But, as I mentioned, would have liked to get the whole kit inside the headlight. It is designed to be installed in there ( see the wire length from relays for example ) , but there is no room in my Iron. Even that the relays are so small, they simply do not fit inside.
If You go this route, get also a high quality bulb. Don't recommend these 100w superhyper bulbs. Just a good brand, high output, normal wattage bulb.
Something like this for example :
http://www.walmart.com/ip/SYLVANIA-9...-Pack/21950005
I don't have this bulb in my Iron, so can't say how good or bad this bulb is.

 

thanks for the link....I think it will fit in my 7" ok. might be a after the riding season project.