KDXRIDER.NET

'03 KDX220
Came with no headlight (replaced with a number plate), tail light (replaced with an MX fender), or lighting switch.

Picked up one of these universal headlights http://www.ebay.com/itm/GREEN-RACING-MO ... 1192882614
35W incandescent with a high and low beam setting plus a 5W incandescent lamp that I assume is a parking lamp.

And one of these Acerbis tail lights http://acerbis.com/prodotto_detail.php?idp=788

Up front, I find these available wires (red and yellow):



And these in back (red and black/yellow):



Voltage measurement on the yellow wire alone was about 49 VAC at idle.

Yellow connected to the red (I believe this is now floating the voltage regulator) was about 3.5 VAC idle, and up to 4.2 VAC with some rev. I did NOT connect either the tail light or head light loads.

In referring to the wiring diagram on page 14-5 of the KDX200 1994 first edition service manual, the yellow wire connects to red via the lighting switch, and the red then powers the headlight and taillight and connects to the regulator.

So, to the questions. The regulated voltage of 3.5 to 4.2 VAC does not seem right and I was expecting to see around 12 volts. Does this seem like a voltage regulator problem? Or is this a magneto problem? Do I need to connect a load to the red wire for the regulator to balance to 12 V?

As a side note, once this power issue is resolved a Vapor computer will be installed. Rewinding the magneto for higher output is being considered but I didn't want to do this yet unless necessary.

You'll have to rewind the stator for all power your going to be using. The KDX isn't DC, so 12v won't read correctly. For the tail light red wire is HOT (+), the black /red wire is ground, I believe the solid red wire is a loop back that turns the tail light on and the yellow is the load from the stator. The switch used to be the ground, using the switch disconnects the ground effectively turning off power to the lights. So you have to ground the head light to the frame. To power the tail light, the Red and the Yellow will need to be connected and then a run to the headlight and then a separate ground will be run from the headlight to the frame.

But I could be wrong and without tearing into my bike I can't confirm this 100%.

The stock headlight is 30W and tail light 10W.
My headlight is 35W (I won't run the tiny 5W bulb) and the tail lights are just a few watts (LEDs). So the stock stator should be sufficient.
You're correct that yellow is power from the stator. However, I don't think the switch is ground. Per the diagram, it appears to connect yellow to red, with red powering the lamps and voltage regulator. The regulator doesn't get powered if the light switch is off. The red up front has continuity with red in back. And the black/yellow wire in back is grounded.

The questions:
1. What is unregulated stator voltage? Is around 50VAC too low?
2. What is regulated voltage without load?
3. Is a load needed for the regulator to operate/test properly?

Wiring Diagram
http://idridr.smugmug.com/photos/i-KNPf ... f2RJ-L.jpg


edit: wiring diagram removed.

Your unregulated stator voltage is going to be dependent on the engine RPMs at the time it is measured, 50VAC @ idle is right in the ballpark. The regulator is itself a load, so there won't be a regulated voltage without load. The regulator voltage when the light switch is on (regardless if there are bulbs in or not) should be around around 12-16VAC @ around 5K rpm if I remember correctly, so 4 VAC at idle may be a little low, but not much. That is the main reason your bulbs appear so dim at idle, but bright at speed. The regulator IS NOT a rectifier, as stated by 6 Riders it's an AC system with the bike frame as the return so you won't get a DC reading of any meaning. (Hence the reason you must float the stator when incorporating a battery which requires a DC system). The Vapor I believe requires a 12V DC system to operate all it's functions otherwise it runs off the internal battery.

I understand this is an AC system. If my posts aren't clear on that, my apologies. Will be testing again tonight with some load to see what the regulated and unregulated voltages are at higher rpm.

Vapor instructions show 9.0 to 400 VAC/VDC. Seems pretty forgiving. Reading earlier threads here indicated some early Vapors had problems indicating incorrect rpm when connected to the system's power and one user just installed a 9V battery. Later posts indicated the Vapor was working fine on system power. We will see what happens . . .

http://gallery.trailtech.net/media/inst ... ctions.pdf
see page 5


Thanks for the replies!!

My vapor is running fine on ac. Irrc, if you move the ground for the tach away from other grounds, the tach reads correctly. Or maybe it's the powers ground that needs to move. I know when I run on battery power, the tach works fine, but using the ac system, the tach pegs almost the whole time, so there is a feedback problem there between the grounds.

Here's an update.

Unregulated stator voltage at idle around 45 to 48 VAC. This is yellow (stator) wire on + side of the multimeter, with - to ground (black/yellow). Revved up it and it passed 100 VAC but not more than about 120 VAC.

Connected yellow to red (stator to voltage regulator) with NO other load; voltage around 4 VAC plus / minus.

Plugged in 35W of incandescent headlight load and the voltage jumps up to 10+ VAC. Rev it up and voltage drops to 9.5 to 9.8 VAC. Rev up and down does not noticeably change light output. Switched between both hi and low connections on the bulb with no difference in measured voltage. Connecting them in parallel drops the voltage and light output (as expected, this stator is insufficient for 70 W).

Why only 10 volts? Is this because a 35 watt load is too much? I'll try a smaller load later and see what happens.