How to convert to LED's and still have everything work

I recently converted my '82 SECA 750 to LED lighting throughout. I did this mainly to save power, since I've converted my bike to fuel injection, and the ECU, fuel pump, injectors, etc, draw a bit more current than I'd like.

Since I was trying to save power, I didn't want to add load resistors; that would have been counterproductive. Instead I needed to make some flasher and computer changes to accomodate the LED's while still maintaining stock SECA functionality.



Part 1 - the turn signals:

This probably applies to most XJ's. The main problem with swapping to LED turn signals is that they draw about 1/40th the current of the stock bulbs. This is a problem because the stock flasher relies on this current for its operation. The stock flasher (with self-canceller) works like this:

It uses a relay with an NC contact and two coils on the pole piece (one about 100Ohms, the other about .2 Ohms). There are also a 1200uF cap and 150 Ohm resistor, but these are actually just to ensure that the turn signals aren't on when the ignition is first turned on. There is no bimetallic element. The stock flasher has three terminals labelled B, C, and L.

Its operation goes like this:

1. The handlebar switch has a two pairs of contacts in each direction. One pair switches conductivity between the Br/W of the flasher and the selected turn signals and leaves it there, the other momentarily connects Y/R and B to the cancelling unit, enabling it.

2. Once enabled, the cancelling unit, which had been holding +12V on the C contact (Y/G) of the flasher relay, lets this contact float. This deengergizes the 100Ohm coil allowing the relay contacts to close.

3. Once closed, the relay contacts provide 12V through L (Br/W) to the turn signal pair selected by the handlebar switch. The current to them flows through the heavier coil and opens the relay. Once the relay is open, current flow stops, so the relay can now close again, and we have a flash cycle, based largely on the magnetic field build up and collapse time of the heavier coil of the relay.

4. Eventually one of two things happens:
a) the cancelling unit's counters expire and it puts 12V back onto the C contact, energizing the 100Ohm coil and locking the relay open (no more flashing), or
b) the handlebar switch is cancelled, which opens the contacts between the L contact (Br/W) and the turn signals (no more flashing)

Anyway, none of this will work with LED turn signals, so an electronic flasher must be substituted for the original one (which mounts under the frame under the tank). The problem is, nobody that I found makes an electronic flasher that will work with the XJ self-cancelling circuit. If you want your signals to still self-cancel, you'll need to make your own:

Actually, you start with a two-pin (or two-pin + ground) electronic flasher. I used a two-pin from Rumble Concept, but I don't like it much since its rate varies considerably with temperature. To adapt the electronic flasher to work with self-cancelling circuit, you need to add another SPDT relay.

Most accessory relays are SPST (that is, they have four pins - 2 coil connections, one common, and one normally open). For this application you need one that also has a normally closed contact (five pins). I used a Radio Shack PC relay, and its working fine, but you may want to get a Bosch-type one that should be a bit more rugged for vehicular use.

Wiring goes like this:
Stock flasher connector Br wire goes to the common pin on the SPDT relay.
The normally closed contact from the relay goes to the supply side of the electronic flasher.
The normally open contact on the relay remains unconnected.
One of the relay coil pins goes to ground.
The other relay coil pin gets connected to the stock flasher Y/G wire.
The load side of the electronic flasher goes to the stock flasher Br/W wire.

I super glued my relay to the electronic flasher, taped up the harness stub, and put a bit of RTV over the terminals before installing the whole thing.



Part 2 - the tail lights:

These are probably easy on most XJ's but are tricky on a SECA 750. I used local auto parts store red 1157 replacements (Jam Straits), though there are certainly better ones available online (SuperBrightLEDs.com for instance).

The reason these are tricky on a SECA 750 is that the SECA 750, and some others, has the on-board computer that checks a number of things including the tail lights. If you don't want the computer bugging you about your tail light being out, you need to modify it. I, being stubborn, not only didn't want it bugging me, but I still wanted the check to work, and I also wanted the check to work if someone put regular 1157's back in the tail light at some point in the future.

The guys that designed this computer were pretty clever. They included two circuits for testing the tail light. The first one checks the current draw of the running filiments in the tail light. The second one checks the current draw of the brake light filiments. Not only does it check the brake light filiments when the brake is used, it also pulses the brake light when the bike is first started (too quickly to see) to do an initial check of the filiments.

These checks of current draw are done in the computer itself. The wiring feeding the tail lamps runs through the computer. Inside there are a .47Ohm series resistor that allows measurement of the current drawn by the running filiments, and a .12Ohm resistor to check the brake lamp filiments. The resistors are the white ceramic blocks on the corner of the computer's circuit board:



An initial guess might be to replace these resistors with much larger values so that they would still drop the correct voltage despite the much lower current draw of the LEDs. The problem, for me, is that that solution would result in burned resistors if anyone ever put regular 1157's back in.

Instead, I replaced these two resistors with rectifiers. Semiconductors have a fairly consistent forward voltage drop that is largely independant of current. The whole process involved some trial and error and I got to disassemble and reassemble the cluster several times, but here's what eventually worked:

I replaced the .47Ohm resistor with a 1N5404 3A rectifier (Radio Shack P/N 276-1144). I had to Dremel down the leads a bit to make a good fit for the stock resistor holes. For the .12Ohm resistor, which needed higher current capacity, I used an NTE581 TO-220 cased rectifier. This is an 8A device. Both of these rectifiers drop enough voltage to indicate to the computer that the LED's are drawing current, but they also can carry enough current to work fine if regular bulbs are ever put back into the tail lamp.



In both cases, the cathode of the rectifier (banded end on the 3A rectifier) goes towards the edge of the circuit board.

Part 3 - instrument lights and the license plate light:

The best power savings by converting to LEDs are obtained for lights that are always on. Two of these are the backlights for the instrument cluster. They're only 7W, but, by converting those to LED you save a full amp of current all the time the ignition's on. That's 5% of the alternator's capacity... nothing to sneeze at.

Since I had to open up the instrument cluster anyway, to make the computer mods, I figured I'd do the lamp substitution at the same time. I also made a new bezel for the warning center, repainted my needles, and cleaned and polished everything while I had the cluster open.

Initially I tried finding some LED 194 replacement bulbs locally. Pep Boys turned out to be the only place that carried white ones. While their packaging claimed to be "brighter than OEM", I found them to be nowhere near as bright as the original 194's. So, instead, I ordered some bulbs from superbrightleds.com. Their prices, selection, and service were all excellent. Besides ordering the white backlight bulbs, I also got replacements for the amber (turn signal), blue (high beam), green (neutral), and red (warning) lights on the instrument cluster, and a white 67 replacement for the license plate light.

http://www.superbrightleds.com/specs/bulb_specs.htm

For the backlights I chose their warm white WLED-WW5 bulbs, and they worked great, very natural and perfect brighness, though they can be a bit tricky to install because of the LEDs sticking out the side. For the indicator lights I used their WLED-x4 bulbs, which actually turned out to be too bright. The green, especially, was blinding. I ended up putting blue masking tape over the green and blue LED's, and regular masking tape over the others. This reduced the glare a bit and also diffused the light so it looks more like the original lighting.



Summary:

So, I now have lights that are at least as bright as stock, will likely last as long as the bike itself, and draw considerably less power than stock. I would estimate that, at idle, and in gear, I am saving a good 48W (4A) of power. Put the bike in neutral, put your foot on the brake, engage the turn signals, etc, and the power savings goes up considerably; the brake lights alone save about another 3.5A over stock when engaged.

Cheers,
Paul

 

Great write up Paul with great pictures too. Thanks!

 

i don't think i am capable of doing this but wish i could.

 

Paul - great work! Now there's a great winter project I can maybe take on because the flasher parts pull right off and the work can be done in the warmth of my shop. Thanks for the inspiration!

 

It's really not that hard if you can solder. Paul did all the hard work figuring it all out...

 

Lo! Methinks we've seen the future of motorized wizardry come to pass.
All hail ...
Kudos - lovely job.

 

i must of been tired or something the first few times i read it.

 

Your whole project is worthy of being featured as a series of articles in one of the many Classic Bike Magazines.
I'm sure there would be ample interest in the Fuel Injection Mod's you've done. The LED conversion is great, too, but could be out of reach for some restorers without the skills to work on circuit boards.

I'm quite sure there are a good many who are doing LED Lighting,, that would like to have a Flasher Unit like the one you devised. That's one of those ideas that could make you a few bucks if you brought the device to market.

 

Paul, The manned mission to Mars needs you. You are the man!

 

i want to do the EFI mod!

tell me more about it...

 

Most of the background of the EFI conversion is covered here: http://residentialcolorado.com/SECA_750i.htm

Since I wrote that:

1. A guy ran my bike over when it was parked in a restaurant parking lot

2. Repairs from that neccessitated swapping to a MAC 4-1 exhaust (nothing else was available either new or at reasonable $$$$).

3. I installed a better duct between the airbox and throttle body, built a new fuel rail that fits better, and swapped in a second set of fuel injectors that I had had overhauled and flow tested.



4. I made a 36-1 wheel to replace the 8-1 wheel and removed the unneeded VR pickup.




I'm still doing some warm-up tuning and accelleration tuning. Sometime over the next few days I should get around to updating the doc with the latest developments.

Cheers,
Paul

 

went to the website...

its WAY over my head...

thanks anyway

 

Looking for a better solution I found this stuff



http://www.kisantech.com/index.php?cat_id=4

http://www.badlandsmotorcycleproducts.c ... BETCSM.htm

pricey

 

Pricey, yes, but also, neither of these auto-cancel systems takes distance into account, as does the stock Yamaha system. These ones are only time-based, so, when you're sitting at a long light, you'll need to keep re-enabling your turn signal.

 

Very nice SQLGuy.

So if I understand correctly you are augmenting the electronic flasher by adding a 12V SPDT Relay?

So aside from removing the old flasher and replacing it with this combo-deal, there are no other changes required for to maintain self-cancelling/flashing signal functionality?

 

Correct. That's it. This combo works the same way, as far as the canceller is concerned, as the original flasher, but, since it's using an electronic flasher, it doesn't have the load requirements of the original unit.

Cheers,
Paul

 

Thank-you for all your help SQLGuy. I put it together and will hopefully be able to test it out soon. But it may have to wait till Spring because although it has been warm in Toronto the last few days, the seasonal temp will return shortly and it's no fun riding in -15C+windchill.

I have pictures of the contraption in my gallery, in case you are curious to see how it looks. It's not the prettiest, and to be honest, my wife warned me about showing it to people for fear that they might think it's some type of remote detonator/etc... but y'all know the deal

I hope it works for me as it did for you.

 

I just finished up converting my tail/brake lights to LEDs and used your rectifier modification on the computer. Everything works great and I wanted to thank you for figuring this all out and taking the time to post it. I will tackle your turn signal/relay trick next, but I think I will pass on the fuel injection, it's tempting but I know my limits.
Cheers

 

Actually, you start with a two-pin (or two-pin + ground) electronic flasher. I used a two-pin from Rumble Concept, but I don't like it much since its rate varies considerably with temperature. To adapt the electronic flasher to work with self-cancelling circuit, you need to add another SPDT relay.


soooo.. i want to get my led blinkers to work with out self canceling. and i am probably dumping my stock gauge. What kind of replay do i need?

 

Just the regular motorcycle two-pin one from superbrightleds.com would work fine, or pretty much any other two-pin electronic flasher. Connect it to the brown and brown/white wires that go to the stock flasher; leave the green/yellow disconnected. You may need to try both orientations (i.e. switch the brown and brown/white wires around) because at least the superbrightleds.com flasher requires the load and supply to be on particular pins.