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NE0

DT 175 MX 12volt conversion

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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.)

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Hey NEO. This may have already been asked but for the life of me I can't find a voltage regulator on my 1975 dt175. I've checked on the air box and everywhere. If i can't find it which wire coming from the magneto should I wire to the regulator pin on the regulator/rectifier?

The battery tray needed a little modification to fit the new 12v battery aka a little love and force but other than that so far so good. 

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Hi akleimer, please remember this is a mod for the later DT 175 MX model. Not the earlier ones. it may be there isn't a regulator fitted? Mine was fitted under the airbox, I've known them to fall off. its only one screw and a wire which holds it there!

Nonetheless, having said that the wire which goes to the regulator is from the ignition switch, the feed comes up from the generator/magneto. Remember also the c90 regulator/rectifier is a combined unit and replaces BOTH of the disconnected Regulator and Rectifier mentioned in the text. One wire from the regulator and two wires for the rectifier are required. I doubt you can connect the 3 pins to the same source!

regwire.jpg

Have a look at the circuit diagrams for the MX if it helps,  but getting a look at the circuit diagram for your bike is a must,  the Haynes manual is a good place to start, as it shows US and UK bikes.

PS it's also good practice to pop over to the NEW MEMBERS area of the forum and introduce yourself, tell us where and who you are and what bike you have etc,

Edited by NE0

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The 75 just uses a big assed resistor, front of the frame on the down tubes, on the Haynes manual isbn 1 85010 300 3  you can see it on the cover on a dt100.

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Thanks Cynic, yes Airhead also mentioned earlier in the thread

Quote

ballast resistors and avalanche diodes fitted to these machines

75reg.jpg

 

and i do like to remind people...this is what i did to my machine! it's aimed at the MX models, it might not always be possible to do it on other bikes.

Edited by NE0

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Thanks for the fast reply. I took your advice and introduced myself in the new members forum. 

I don't remember seeing something like that resistor on my bike but I'll check for it next time. 

I guess I'll have to get my hands on a Haynes manual for the diagrams. I have a clymer manual but when it comes to the electrical system it's not much help. And most of the diagrams I find online are for bikes with multi stage key switches. Mine only has two stages (on and off)

I know this guide is for a different bike but this is the best right up I've found for a bike that is at least similar to mine so I hope I can reverse engineer it to work with the dt175. The first problem I ran into was the new battery not fitting in the tray attached to the oil tank. A little bit of work to the tray made it fit though.

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No. That's the earlier manual. The one I listed also has the mx details. Also quite a comprehensive wiring section with diagrams of most ft wiring. Both us and Europe. 

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Ok I cant find anything by isbn but judging by the bike on the cover and the Picture NEO posted and the fact that this one is to 1985 and not 1980 this should be it:

Ebay.com

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I just wanted to drop in and say thanks for all the info in this thread! I picked up a '77 DT250 for cheap a few months ago, and have been working on getting it back on the road.  I wanted to updated the lighting, and found this thread.  I picked up the SH570-12 Reg/Rect and the Motobatt MB3U, as well as all LED signals, relay and head/taillight.  Finally got it all wired up and it all works as it should! I even got the 30/45w LED headlight to work with no issues off the dc/battery circuit, and still have enough power to keep the battery charged with no issues!  Have a Trail tech Vapor wired in as well with a working indicator dashboard!
Here is a short clip of it running!
https://www.youtube.com/watch?v=cReT6Znp1g0

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Hi there, Well done that man, always nice to know about another succesful NE0 Conversion!  Nice to know you've also adapted it with the headlamp run off the battery, which to be fair is not difficult to do, just has to be wired up to the battery instead of the generator. its also great to know the battery is coping so far with this addition. 

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Yes converting the Headlight to DC was super simple.  Just making another lead on the brown wire from the ignition switch and running it into the Yellow wire on the headlight switch.  I had it on the AC circuit originally, but there was really bad flicker with the LED, which I figured was really bad for the light itself.  I also bought a relay timer I am going to attempt to wire into the system so that the Headlight is only on when the engine is running, or for 15 seconds after it is turned off.  I also connected the White wire to the Yellow/white wire so that the regulator was still in the circuit.

Edited by clausenfoto
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Hi guys

Thank NEO the information is GREAT. I am part way through the conversion.

My bike is 89 model, so in Australia it was only another year before they were 12volt anyway, the key only has Lock, off and on positions. the headlight only came on with the engine running in 6volt form, but the taillamp did light up with engine not running.

I have the bike running, it seems to start aersier on 12volt than it did on 6volt, possibly more stable spark, voltage is good even at low revs.

The problem i have is that i have 0volts at the headlamp connector. what have i missed?

Good Riding Brett

I have just rechecked the headlight I have 6.4volts AC at idle.

Edited by Aus Brett
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Hi Brett, welcome to the club, nice to hear the 'ol 12v conversion is still being read.

The write up was aimed of course at MX models 10 years earlier than yours! so it may not entirely apply as the wiring is likely to be a little different. However, I guess if you've got so far you've taken that into consideration.

if it was an MX I'd be thinking......

Is the 6.4v at idle without the effect of the regulator/rectifier in the circuit?

This would be expected as shown in the 3rd post on the first page of this topic   it would then go up as you rev the engine. As explained the purpose of the 6v regulator was to clip the voltage to 6v regardless of the output. Fitting a 12v one in essence clips the voltage to 12v instead of letting it get to 14v etc...

if you're saying its 6.4v regardless of the revs then I also might be thinking you've got the 6v reg still in the circuit or the one you bought is a 6v one or faulty. Having said that, all this applies to the MX wiring circuit and may not apply to later models.

Earlier models of DT have fancy things called avalanche resisitors and whatnot!  (as mentioned by Cynic and Airhead in earlier posts) so it's not unreasonable to think you may have other accessories in the wiring which might effect the results.

You also mention the tail-light  lights up without the engine running, Well that is the same as the DTMX as its only the headlamp and charging circuit which runs off the generator. Everything else: indicators,brake light,tail light and horn all run off the battery.

This may be of some help to you but equally just proceed with caution. Good luck

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Thanks for getting back to me NEO.

Just checking that i have followed the instructions, you are only connecting one wire to each terminal on the rectifier regualor?

I cant find an actual wiring diagram for this bike. but looking at others close to it there is either "control unit" or a relay that keeps the headlamp off until the engine is running. that would appear that the headlamp is never part of the rest of the bike, so i will either need to bring the yellow headlamp wire into the reg rec. Does that sound right?

Good riding Brett

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Hi Again NEO

Lets see what we can make of this, whether I have followed the instructions correctly.

The wiring diagram that I have is for a 1990 DT175. available from (removed- Cynic)

The 89 manual does not have a wiring diagram.

Pages 10-1 and 10-2 are the diagram.

I have taken the red and white wires from item 6 Rectifier to the rectifier side of the C90 rec reg, and the yellow with white trace from item 14 Regulator to tye regulator pin then the fourth pin to earth. your instruction say the yellow wire so should that be the yellow wire coming from magneto item 17? If so wht happens to the yellow white wire that goes to the old reg?

Thanks for your assistance

Brett

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I can't stress this enough but the colours and procedure is for the DT175MX range for the late 70's and early 80s models.

Its unlikely that the colours used on the MX are an exact match to colours of another wiring diagram even if its built by the same company!

so bearing that in mind, The C90 regulator uses three wires and an earth (dont forget the earth, the body was earthed to the frame on a MX bike, the C90 body is not earthed from inside, it uses the terminal)

The C90 is wired using the two wires which went to the rectifier (red and white on 1978 MX) to one side. The other side has the earth and what ever wire connected to the regulator on the other side.( yellow on a 1978 MX, yours may be a different colour!)

I don't have your circuit diagram in front of me but if you're saying the yellow/white wire went to the regulator then that's the wire which goes to the C90 combined reg/rect.

 

The wiring colours below are those of a 1978 DT175MX....yours maybe different.

regwire.jpg

 

Edited by NE0

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Brett it may be useful for you to locate a DT175MX 1978~1982 wiring diagram and compare the layout to yours.

However, the headlamp is run from the generator on an MX bike (1978) There are no circuit breakers or resistors or control boxes etc. it's a very simply wiring circuit/diagram. The ignition switch controls the circuit.

Positon OFF : Engine off. Light circuits OFF

position I : Engine running . switched lights only (indicators horns brake light) no headlamp.

positon II : Engine running . All switched lights above plus  HEADLIGHT AND TAIL LIGHT ON  (today this would be called daytime running also)

position III : Engine off. Tail light and parking bulb in headlamp ON ( Key can be removed from ignition bike left with minimum lights on for parking up at night)

 

Here it is: once again colours are for a 1978 175 MX UK bike.

dtwd.jpg

 

the Ignition switch internal contacts are the black bars and dots.

in position II the red wire from the battery is connected(by internal contacts) to the brown and red/blue strip lights/indicators etc.

Whilst at the same time the yellow wire from the generator lighting coil goes to the yellow/purple of the headlamp and also to the regulator which 'clips' it preventing overvoltage to the lamp (a 6v regulator will clip it to 6v for a 6v headlight whereas a 12v regulator 'clips' it to 12v when a 12v bulb is used.)

Also the generator white wire goes to the rectifier which in turn goes to the battery and charges the battery. It is noted that the white wire also goes to the  switch but in postion II it is not connected. (In position I it helps prevent overvoltage to the battery.

 

 

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