DT 175 MX 12volt conversion

[NE0]

And here's the same circuit with the modification. Note nothing else has been touched.

Edited September 30, 2018 by NE0

[Aus Brett]

Thanks NEO

We are now running and offf for a blue slip tomorrow morning.

Does your bike have AC or DC to the headlamp? Mine has AC still but a 12volt H4 55/60 watt lamp is working.

I have made other little changes on the way such as a DRL/LED blinker setup, LED instrument lights. The telltale on the blinkers needed to come out, will modify that light socket once we get rego sorted.

The old girl lives again.

Good Riding Brett

[NE0]

Good to hear you're up and running Brett, Nice one.

As regards to the output at the headlamp, Here's a little tip for you especially if you don't understand electronics etc.

Batteries produce DC wheres a Generator will produce AC. (I know some bright spark may pipe up and say about Invertors and Commutators, which are generally expensive devices to get AC from a Battery and DC from a generator BUT you wont find these on a little DT motorbike!!!)

As you're working in the headlamp shell you will find both AC and DC. However, only the headlamp bulb is fed from the generator so it's the only one which is AC. All the other wires will supply DC from the Battery. And to supply the headlamp with AC the generator needs to be running. Turn off the engine and the AC stops....the headlamp goes out!

Hope it helps,

Well Done mate!

Edited October 1, 2018 by NE0

[rentaspoon]

Hello, 

Glad to see this conversion still gets some use out of it, I'm actually looking to rewire my RS100S to 12v this year so glad that this is still up.

wiring is basically the same.

Green or Green+Red to white to charge

Yellow to headlamp

From what I understand the DTs have a wire that comes off from the switch to the regulator as well as to the headlight? It's the only part I don't understand in the guide

Pic of my wiring just because.

 

Also looking at removing the yellow wire and running the headlight off the battery since the other lights do. Might just terminate the yellow wire straight to the regulator since I can't see it doing harm 

Edit: The other options are using a 3 phase regulator as this will either use a smoother output or more voltage to regulate (which requires a regulator with a better max wattage rating) unsure on what but if I had to guess I'd say its smoother, final option is a single phase rec/regulator with a capacitor.

Edited January 27, 2019 by rentaspoon

[NE0]

Quote

From what I understand the DTs have a wire that comes off from the switch to the regulator as well as to the headlight? It's the only part I don't understand in the guide

Hi there Rentaspoon,

I thought I wrote it quite clearly but let me recap:-

look at the key positions marked I, II and III          *****READ THE ROWs ACROSS****

key position I;  The red wire goes from the battery and is switched to the brown (This goes to the indicators, brake light and horn) The headlight is not lit up on this key position.

Look at the GEN. the white wire (charging wire)  goes to the reg/rec and then onto the battery to charge it via the red wire the other white wire comes to the switch. We know from the first page posts that the OUTPUT of the generator on the WHITE wire is anything from 11volts to 26 volts (depending on revs) This amount of voltage would fry the battery. So it is connected BACK to the reg/rec via the YELLOW/WHITE wire (on the right side of the pic) to 'clip' it and reduce the current going to the battery to charge it

This will cause the reg/rec to heat up and the fins help dissipate this heat thereby cooling it down.

 

Key position II:  The red wire goes from the battery and is switched to the brown( doing the same as above) and is also switched to the red/blue wire (This  ADDS the tail light and pilot light)

The GEN white wire is still connected to the battery via the reg/rec BUT the white wire which goes to the switch NOW does nothing because in switch position II it is NOT connected. (The battery is still charging but the output on the white wire has been reduced because the lighting coil inside the generator is now being used)

So now look at  the YELLOW wire from the GEN ( on the left)  This carries the output of the lighting coil to the headlight. It is switched to YELLOW/RED wire to run the headlight. BUT we also know from the first page post the the OUTPUT on this yellow wire is anything from 6v to 16v depending on the revs. Prior to the conversion the headlight only required 6 volt. ALL excess voltage was reduced by reg/rec on the YELLOW/WHITE (right side wire) The reg/rec clips the output to 6v otherwise the output would blow the bulb.

Using a different 12v reg/rec, this clips the voltage to 12volt enabling the 12 volt bulb to be used in the headlamp instead of 6v The right side YELLOW/WHITE wire is still connected to the reg/rec and the unit still heats up as above.

Unfortunately, the generator STILL produces 6 volt at low revs, because the generator has NOT been altered/replaced. therefore at low revs the 12volt  bulb will glow dimly on 6v output. It only glows brightly once the generator produces 11volts plus.

 

Does that help?

Edited May 29, 2020 by NE0

[rentaspoon]

OK I think I understand, both my wiring goes to the switch first whereas yours goes to the regulator instead. 

Pretty sure I can figure it out now

[Bob Adam]

Excellent thread and has inspired me to do the 12v conversion.  I have got all my stuff from "speedshop" and just about done. The regulator is easy to find on my 1981 dt175mx however I cannot locate the rectifier, can anyone help me with this. I think it is under the tank on the left handside but as that is so small I am not sure - it has a red and two white wires going to it. 

[Cynic]

That's the one.

[Bob Adam]

22 minutes ago, Cynic said:

That's the one.

Thank you so much

[NE0]

Good Lord!! Can't believe people are still interested in this thread!! and it's had 82.5K views!

Looks like Cynic has come to your assistance Bob, hope it all goes ok. You'll be pleased to know my conversion is still going strong albiet the DT is now resting on SORN having moved a few weeks ago. The plan is to change its taxation class to 'Historic' with the change of address then I can start using it occasionally. Nonetheless I rode it on and off  the removals lorry! and the headlight was working fine.

[Jey]

On 5/3/2018 at 11:45 AM, NE0 said:

Hi Guys, i know I haven't been around for a while but you'll be pleased to know I'm still around and so is the DT. The 12v conversion is still going strong and has remained trouble free and reliable, and because of that , technically there's nothing to report.

A few months ago I retired and subsequently the DT is no longer being used as a daily commuting bike (which was the reason for getting it) It's currently SORN only because the MOT centre closed down and I've yet to sort it out, just got so many other things on at the moment!

(Having said that I'll end there as I don't want this thread to go off topic as it seems to remain a popular post to read.)

HI NE0, 

Thank you very much for your write up on this, you really saved us. 

I did the conversation to the letter as you described, everything works well except the headlight. 

The head light is still dim and it seems that the battery is not also get charged. 

I could only find a RnR compo made in China, would you be able to say that's the problem is because of Chinese RnR. 

I have got a Honda genuine RnR and going to play again, will update you as well. 

BTW, mine is a 88 DT 50LC

Thank you again for your time and efforts here. 

Best regards, 

Jey from Srilanka 

[DaddyVet]

Hello! I know i know im 11y late to the conversation but maybe someone is still around to help?

 

I am trying to convert my 1978 DT175E to run 12v LED head and tail lights. Any advice would be amazing. Im in the US so idk if the rex conversion is financially the best option. Ive deleted the battery already and the ignition i just want to be sure i use the right regulator/ rectifier and don’t burn up my bike. 
 

here are some things i found on amazon that I believe might be the right idea, if anyone can verify for me?

https://www.amazon.com/SUPERNIGHT-Converter-Electronic-Transformer-Waterproof/dp/B07H23J6WG

 

Edited March 20, 2022 by DaddyVet
Spelling error

[DemonDriverDan]

Apologies for bringing up an old topic but I'm attempting this change on my DT125 MX shortly and wondered if anyone had a copy of the wiring diagram for the new rectifier / regulator? The links for me seem to be dead.

Thanks!

[NE0]

Hi there Demon, I'm the original poster for this topic and all the pics i posted still work as i keep them active. You might want to try another browser or PC.

Theres no internal wiring diagram of the insides of a regulator/rectifier if thats what you are searching for, just my diagrams of where they go within a 175MX diagram.

 

[DemonDriverDan]

You're correct, my apologies! The forum made it look like the image links where dead but actually worked fine when I clicked.

Thanks!

[DemonDriverDan]

One more question from me. I’ve wired everything in and all seems to be working apart from the headlight. I can see I have 12v AC going to the bulb holder when the bike is running however the bulb I have is not working. 
 

This is the bulb I ordered: https://yambits.co.uk/12v-3535w-ba20d-headlight-bulb-p-137616.html

Does anyone have a part number or details I can use to try another bulb?

[NE0]

if you've got 12 v at the holder ...I'd simply check the bulb across the battery terminals to see if it works, if it does, then you need to be looking at the headlight bulb holders earth wire, with a bad earth your bulb won't light up.

[DemonDriverDan]

Thanks NE0. The 12v AC I was getting was using the earth wire of the bulb holder but I’ll try again in the morning. I’ve tested the bulb using 12v DC from the battery and that worked ok so the bulb itself isn’t broken. As an additional test I’m going to put the 6v bulb in and test on idle, from my understanding it should light up as my readings see about 5.8v there. I’ll keep testing!

[NE0]

Unbelievable!!

I've just been looking at the stats and this post has now surpassed 135K views making it the most viewed topic in the Workshop Section of this website.

Hopefully, its been of some use to you all 6 to 12volt converters. I started this post back in 2011, and here in 2024 its still going strong on my DT175MX.

In the next few months I'm going to ask the mods to lock the topic, as I don't think there's any more to add from my point of view as all the information for a successful conversion is contained herein,and little has been added in the past few years.

In future If anyone is having trouble with their own conversion it would be sensible to start a new thread for their bike and reference my post within the subject and where you might be having the trouble.

Keep on tinkering!

NE0.

 

[Snakebite68]

I can lock it if you want NEO, but, maybe we need a 'How To' section and you could transcribe the important bits there?