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Discussion Starter #1 (Edited)
Hi all, first post, I've read a lot on here and appreciate all of the knowledge shared.

Thought I'd share how I modified my '87 to easily work with an H4 Hi/Low LED bulb, eliminate headlight strobing and brightness variations with RPM changes, and turn on the headlight with the key like later TWs.

If you look at the attached diagram, there is one coil that powers both the headlights and the rectifier/regulator that charges the battery. The headlight is powered directly off the coil prior to the rectifier, meaning the headlight is getting AC power, which is not ideal for LEDs as they only pass current in one direction. The 20W H4 LED bulb I have worked without modification, but it was very dim at low RPM, and had a lot of strobing since it was functioning as a half wave rectifier.

Anyway, what we want to accomplish is to power the headlight with 12V DC from the ignition switch similarly to the tail light. To do this we need to splice together the wires marked 1, 2, and 3 on the attached diagram. You wouldn't have to do 3, but it's easy and allows you to run an LED speedometer light more effectively (brighter).

The process:
1) Remove the headlight assembly from the bike by removing the fairing and the two hex bolts on the sides of the light.
2) Splice a new wire onto the brown wire right below where it exits the ignition switch (location 1 on the diagram). I used a quick splice with about 6" of new wire.
3) Unplug the blue wire (location 3 on the diagram) at the bullet connector inside the boot next to the right fork leg between the triple clamps.
3) Cut the yellow/red wire 1" above the plug, inside the boot next to the left fork leg between the triple clamps (location 2 on the diagram). Cover the end of the y/r wire that remains on the plug with a cap, or tape, or something as it's a hot wire that's no longer used.
4) Twist together the stripped ends of the new wire added in step 2 and the yellow/red wire coming from the headlight hi/low switch, and crimp on a female bullet connector.
5) Plug the male bullet connector on the blue wire into the female connector you just installed.
6) Organize the wires and reinstall the headlight and fairing.
7) Ride.

A few notes:
1) Use a bulb of reasonable wattage. I wouldn't go above 20W as I'm trying to be conservative with this old charging system, and there is some efficiency loss by running everything through the rectifier/regulator. I've replaced all bulbs except turn signals with LEDs, so I'm confident my overall current draw is low enough the charging system will be fine, but your setup may differ.
2) Make sure you understand the general concept before proceeding with this mod. It's easily reversible, but not if something gets blown or shorted.
3) This is only for 1987 TW200s, later models have different electrical systems.


87 TW200 Wiring Diagram.jpg
 

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Discussion Starter #6
And have a spare reg/rec and a main fuse with you – lol - but yeah, it works in principal

Welcome to the board….. ;)
Thanks Purple, you may be right, I've only got a few hours on it since I did this. What I've found online has suggested the stator is the weak link, but I'll keep an eye on the rectifier/regulator. Since you seem familiar with this issue, what continuous amperage is the '87 rectifier/regulator good for? At any rate, an LED tail/brake light and headlight are probably mandatory if the rectifier/regulator is as marginal as you suggest...
 

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Welcome, and thanks for sharing. I have an '87, and don't need this mod just yet, but am appreciative of your efforts.
 

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Discussion Starter #10
Did a bit more measuring this morning. My headlight is more like 30W. Total engine off/key on electrical load (LED head, LED tail, and LED speedo lights, and whatever the Ignitech CDI draws) amperage is about 3.3 amps, and total rectifier output with engine above 4k RPM is about 3.5 amps. Rectifier/regulator is barely warm to the touch after a 15 minute ride. Still confident this is going to be fine over the long run, but will update this thread if I run into problems.
 

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Discussion Starter #11
Around the 8 amp mark – the ’87 is single phase, so you might be putting more strain on it, but just how critical that actually is remains to be seen. There are a couple of good threads that cover this …
Thanks Purple, good info there, especially the second thread.
 

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i did something similar to a 1981 honda ct110. one difference with mine was, i took your unused headlight ac wire and added a second rectifier and feed it to the battery. i never had an electrical or battery problem again. another difference with mine was my bike didn't have a voltage regulator, but alwas having the headlight on kept the voltage in check
 
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