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Part3 The lighting coil Let there be light. My Dt has three coils, Two source coils which are attached one on top of another and are part of the CDI (electronic ignition) One of these creates the spark at low revs the other at higher revs. Used together this way, maintains the spark across the revs range. The other coil is the lighting coil. It has two windings over one core. One winding terminates as a white wire and is responsible for the charging the battery. The other wire, the yellow wire runs the 6v lights. Because it’s only a small coil, (12 volt coils have more windings) it’s output is limited. Nonetheless, it will still generate 12volts. The trouble is you don’t get something for nothing and it takes a lot more revs to do so With the engine running and the generator disconnected from the rest of the bike, the output is as follows: Read the RED scale on photo below of the meter for AC volts. Yellow wire (lighting circuit) 2000 revs = 6v 4000 revs = 11.5v 5000 revs = 14v 6000 revs= 16.5v It’s the function of the regulator to ‘clip’ the voltage to 6v thereby maintaining the 6volts across the revs range. White wire (charging circuit) 2000 revs = 11v 4000 revs = 18v 6000 revs = 26v this wire is the charging circuit and it too is clipped by the regulator so the voltage remains steady. This circuit also runs through the rectifier. This device can be likened to a one way valve and ensures the voltage only goes in one direction to charge the battery. So it can be seen that there is 12 volts output from this coil, but you need higher revs to get it. the other factor is that changing the regulator to a 12v means the voltage will be clipped to 12 volt above 4000 revs hence the reasons the lights go dim on tick over and up to about 3500revs. (you can’t tell 11v from 12v) In theory you could run the lights off the charging circuit and use a 12volt regulator to maintain the 12 volts, but you wouldn’t have anything to charge the battery. Having said that you could simply run everything off this circuit without a battery! I might give it go just to see what happens!! READ THE BOTTOM RED SCALE FOR VOLTS Reads: 0-5-10-15-20-25-30 Part 4 next, any other options before we start!

Part2 A bit of theory Einstein. Any concerns about wiring.? Will the wiring for 6v be ok for 12v? Yes it will. Its all to do with amps and a few electrical laws Do you recall at school, you only needed any 2 values to get the third? Volts = watts divided by Amps V=W/A Amps = Watts divided by Volts A=W/V Watts=Volts times Amps W=V x A Not very inspiring is it? Let me apply it to the DT. The main headlight uses a 6volt 35w bulb As we have the watts and volts, so we can use the above equation to work out the Amps it uses. This can be written as 35W / 6V = 5.8Amps so the wiring deals with 5.8A simple? Eh? Therefore, if you replace the bulb with a 12v /35W one. 35 w / 12v = 2.08 A The Amps loading is half and subsequently the wiring does not need replacing. Of course you need to add up all the bulbs on the circuit to get the total number of amps the wiring has to cope with, but it will always be half the amps the 12volts needs when compared to 6volts. Or you can look at it another way in fact 6 volt wiring has to cope with MORE amps than 12v. Clear as Mud I hear you say!! Trust me this is how it works, the wiring will be fine. However, My DT175MX's wiring is now over 30 years old and one of the reasons it failed the MOT was poor earthing. Unfortunately, it wasn't just a clean up of the frame ground which allowed the lights to work again. I had to clean up EVERY contact. All the connectors were badly tarnished, the wiring in places is quite brittle and on closer inspection the copper wire has gone green. This increases the resistance of the wiring and means the electrical flow will be impaired adding further problems. All these are signs that over 30 years the atmosphere had got into the copper and oxidised it. At the end of the day, nothing last forever, and the 30 year old loom will need replacing. I'm only replacing mine because its old and the resistance is higher, but all the conversion was done on the existing loom. Part3 next..the lighting coil

My plan was to convert my DT175MX from 6 volt to 12 volt and if it worked then do the write up. However, a fellow DT rider, kiln was also doing something similar but had only upgraded the regulator and bulbs. So I brought forward the write up but the project is not finished yet and I can't say that it works 100%. (as I've not had enough time to evaluate the success.) I may have to edit this post in the future! i can say it works 100% I updated the topic after 9 months of use at the end. Disclaimer. This is what I did to my own bike, i can't be held responsible if you fry your electrics or your own bike if you try repeating it. It's up to you to satisfy yourself that the advice, solution, method is right for your bike Part1. Why ? As many of you will know the DT175MX and I'm sure many other bikes are 6volt.There are many reasons why manufacturers use 6v instead of 12v They don't fit 6v for the fun of it, after all they spent their money doing the research. However, a lot will be to do with physical sizes of the generator itself and to some extent the space available for the parts to be stowed on the bike. The late 70's, early 80's DT range is one of these bikes. It has a physically small generator in comparison to other bikes around during this period. Many bikes of this time were 12volts, but their generators were much bigger, afterall you don't get something for nothing. The good news is time changes many things. I can't imagine many new bikes today are 6volt, advances in Electronics and technology will ensure you don't ride around in the dark! Some guys in the past have tried to convert their bikes to 12v some clearly fail and some no doubt succeed, I hope to be one of the latter! I purchased my DT175MX at the beginning of 2011, two weeks later it failed its MOT...on the lights and horn. They were not adequate for the test: whilst the indicators did indeed flash, the brake light thought it was an indicator too. The horn sounded like a fart, and not a very loud one at that! The culprit was poor earthing, but once fixed it did all work, but it wasn't a sound and light show. The MOT guy suggested converting it to 12volt to avoid problems like this in the future and was confident there was probably a 'kit' somewhere which would do the trick. Sadly, after many hours of trawling the net I couldn't find one. There are indeed plenty of 12v conversions for other bikes, just not the smaller DT range, but one thing's for sure they weren't cheap either!! I then spent more hours trawling the net and came across the post in the forum about the guy who swapped his magneto over for one from a 12volt Honda C90 cub, Take a look here the trouble was he never finished the write up and never said it worked without any problems..maybe he set fire to his bike in the process. Nonetheless, the very fact that a modern 12volt system could be, in theory, transplanted into the ageing DT filled me with inspiration. I set about doing my own home work and started project 'firefly' (Small glow-worms which emit very small amounts of light just like a DT175!) Part 2 to follow

Hi guys I bought my DT as a winter commuter bike, Its being well used in all weathers, and I've clocked up over 280 miles already and I've only had it for 6 weeks. Now I'm looking at putting a rear rack on it for my works bag and chain etc, might even put a removeable topbox, but first i need a rack. I guess the chance of finding a new one specifically for the MX will be remote, nonetheless I thought I'd ask. Does anyone know if a another rack for another bike just happens to fit? or is it a case of make your own/DIY? or any other ideas. I found this photo on the net, i don't think it looks too bad at all. However, before anyone says don't do it, use a rucksack etc, my bikes not going to shows or anything. Its stricty a working bike, it's unlikely to go green laning, and i've had enough of my rucksack!

£1.80.. I didn't even get that as change from a tenner! in fact i got £1.20.. I must have been running on vapour! Nice to know the mileage is expected. I'll keep on eye on the mileometer! ...and I MUST remember to keep the oil tank filled up. I assume it will need to be topped up around the same time as the fuel?

Hi Guys Been using the new bike for a few weeks now , rain or shine...mostly rain!!! Got unbelievably soaked on Saturday during a 40 minute downpour, but heh I'm using it! However, it didn't help when it died at the lights! thinking it was the rain I was frantically kicking it over much to the amusement of the car drivers behind me, although in the downpour I'm surprised they could actually see me. As I rolled it over to the kerb I noticed the mileometer (odometer if your pedantic ) with 90 miles, I remembered I did zero it when I filled up last, a quick turn of the petcock to reserve and it sprang into life!...and it was still chucking it down. Good old DT. I don't know how big the reserve is so I filled up at the nearest station...just as the rain stopped! So I was just wondering how many miles do you fellow 175MX riders get, is 90 about right? less? more?,

Well Guys you certainly know your stuff. My bikes cured!!! All three engine mounts were loose, the back top one was only finger tight! the other two were not as bad, all three have now been torqued up. Plus the swinging arm nut was not as tight as it could be, nearly a full turn before the torque wrenched 'clicked' I guess the clues were there in my intro , the frame had recently been stove enamelled, like past 6 months and clearly whoever did the work didn't tighten it all back up again. this prompted me to check all the other bolts , one bottom fork nut was also loose! All in all I'd say the vibration was 95% gone. It's not as smooth as my 400/4 so my expectations are it bit misguided! I expect you get a slight vibration from a stroker (trouble is its been 34 years since I was 16 and riding them!) But I'm a happy man again! so the drinks are on me , what will you be having guys?

Thanks for the quick replies guys, Neither of you wanted a pint then? I'm not over keen on taking it off the road just yet to rebuild the engine having only just got the bike. So I won't be stripping it down in a hurry and even more so when I don't need to.. I will check those items tomorrow and get back to you all, (providing I can get the time!) some more details for you... Cynic, it is only noticeable on throttling or cruising, soon as you throttle off and remove the load on the engine the vibration stops. On tick over it sounds just like any other stroker. I did wonder if it was speed related so i took it out this afternoon, and no its not. You can ride at 20 or 40 an its only noticeable when the engine is throttled up!! (Gee isn't that what happened to the shuttle Challenger? you are clear for throttle up....Kaboooom) cut the revs and it goes. Its quite a harsh vibration which you feel through the pegs first and then it feels like it makes the frame vibrate. Don't get me wrong its not shaking, its a rumble vibration. I did take out the plug a few days a go just to check , it was not oiled up but a nice brown. Its not difficult to start, one or two kicks, but certainly harder if the engines hot. If any of this helps? Cheers...don't forget your pints guys....

Hi guys, I’m up at the bar looking into the bottom of my empty glass! Let me buy you a drink, and tell you the problem with my DT175MX I’ve only recently purchased it to go with my CB400/4. see both bikes here It’s a 1978 registered early 79. Its got 19,300 on the clock, seems genuine as it came with MOTs dating back past 20 odd years. It had a rebore at 14,300 including 2 main bearings (not the big end). In the past week or so I’ve noticed it has a rumble under load, it’s a vibration which travels through the foot pegs, take the revs off and the rumble disappears, go back up through the gears and it becomes more noticeable. I’ve only had it a few weeks so in all the excitement I may have not noticed the rumble, but as I’ve ridden it more its certainly there! My thoughts are is it’s the big end….... So what will you have?

Welcome Budunt, Not the greatest start but credit where credit is due...this thread has the HIGHEST number of views in the Noob section well done.

Many thanks for the welcome. If it’s of any value to those who have an interest in numbers, the frame/engine are in the high 3900’s so If it started at 000001 its under the 4000th made! , It was registered in early 79. It’s got the characteristic round tube swinging arm, and the smooth side panels. There’s also a short front mudguard which causes spray all over your chest in the wet. On the back is a rubberised mount for the tail light and plate. It passed it MOT today…horray , but it did fail a few days before!! The frame has recently been stove enamelled but the frame earth was not cleaned back to bare metal, so all the lights were dim and flickering. A good clean of all the contacts and a good frame earth ensured a pass today. I’d like to convert it to 12volts and read with interest the post in the main forum of a conversion but the thread was unfinished. I’ll keep doing my homework but its certainly on the to do list….eventually! The 400/4 is my pride and joy and I restored it to its present condition about 10 years ago, I’ve kept it nice and have on occasions showed it at local transport festivals. If I could find away of riding both together I could show the DT along side it! All the best NE0

Hi folks, Just saying hello to you all Recently got myself a DT 175 MX to go with my Other bike! I've owned my 400/4 for over 25 years, its a lovely ride but up until recently I'm not so keen on getting her wet, all that chrome takes a while to polish and the road salt doesn't do it much good either, so from now on its a summer / dry weather bike. However, I wanted a commuter/wet weather bike so I bought a DT 175 The idea is the 175 will be my winter/wet bike. Don't worry folks the 175 will be kept just as nice as my Honda! Here's a picture to wet your appetite for the 70's NE0