@Elan-n Have you done a full carb clean including the emulsion tube?
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HOTSHOT III
@HOTSHOT III
Posts
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Jetting the carb -
Newbie@madmackie No worries
If you get the P45T bulb in the link it should fit straight into the light/wiring, P45T fitting is similar to the more common H4 but not identical. I don't know of any other Yamaha that uses P45T bulb fitting but every DTR I've ever owned has had it. Copied and pasted from Google AI Overview:P45T and H4 are both dual-filament (high/low beam) headlight bulbs, but they differ primarily in their base diameter and application. P45T features a large 45mm round base often found on older classic vehicles, while H4 (specifically P43T) has a smaller 43mm base standard on modern cars.
Key Differences:
Base Diameter: P45T is 45mm; H4 (P43T) is 43mm.
Application: P45T is used for older, vintage European cars and motorcycles. H4 is for modern vehicles.
Interchangeability: They are not directly interchangeable, but adapters exist to fit H4 bulbs into P45T housings.
Performance: Both come in halogen, but H4 is more commonly found in higher-wattage, brighter variants.Summary Table
Feature P45T (R2/H5) H4 (P43T)
Base Shape Large Round Smaller Round/Triangle
Base Diameter 45mm 43mm
Vehicle Age Classic/Vintage Modern
Availability Harder to find Ubiquitous -
Newbie@Calum Thanks bud, I'd like to do more of them!
Now I'm no longer interested in riding it opens up the possibility of approaching bike builds dispassionately as engineering projects and I have a few ideas.
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Newbie@madmackie I never bought a headlight cowl from BPS but the shrouds, side panels and mudguards I always found shiny and an extremely good fit.
I did get a few pattern headlight cowls from an eBay seller in Germany, they weren't as shiny as OEM as you say and I also had to modify them to make them fit perfectly as the part where you're supposed to drill the mounting holes doesn't extend far enough back. I found the neatest solution was to just cut off that part completely, make up some small tabs out of stainless steel and this enabled me to get the holes in exactly the right place.
With the headlight cowl, the biggest visual impact comes from getting it to fit around the headlight and front mudguard perfectly; this part of the bike looking "bodged together" leaps out at you. Another mistake people make is fitting the clocks above the upper fork clamp, then wondering why the lower headlight bracket mount (on the lower clamp) doesn't line up; this results in a huge gap between the cowl and the mudguard which screams "lack of attention to detail" from every angle.
With the German eBay headlight cowl modded as described above, I often rode my DTR to local Bike Nights where it generated a lot of "you don't see many of those any more" kind of interest, and no-one ever noticed the home-made mounts; people only really see what they want to see and with the graphics applied, clean bike etc. it's the overall effect that turns heads.
I do understand people wanting to make their DTR look perfect but equally there is a danger of the classic car "concours" mentality (they use shoe polish on the inner wheel arches!) detracting from one's enjoyment of the bike; Yamaha never really meant for the DTR to be like this and part of the enjoyment is knowing in one's own mind that the bike is as good mechanically as it can possibly be.
To this end I would focus on the following (others on the forum will tell you I always say this lol):
Run genuine clutch and throttle cables; these are extremely good quality and worth every penny, and the throttle cable on early bikes like yours (judging by the shape of your oil pump cover) has a mechanism which balances the carb and oil pump automatically.
Buy a cable oiler (£4.99) and keep them lubed after every wash for striking cobra responsiveness. A bit messy but again well worth it, Comma Spray Grease works well:
Get a really good grease gun and keep lubing the rear suspension bearings.
Run a really good quality (D.I.D) non-O-ring chain and sprocket set; a sealed chain takes an extra 1/2 a horsepower to turn which makes even fully derestricted 125s feel sluggish. Unsealed chain requires a bit more timely maintenance but it's worth it for the riding experience.
Run a 100/80W halogen headlight bulb; the DTR has AC lighting which means it can handle this without flattening the battery unlike a lot of bigger bikes. This gives you rally car lighting and retains an MOT-friendly beam pattern:
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Newbie@madmackie That bike looks ace, I've never seen that graphics kit before anywhere.
I think if it was mine I'd be getting another fuel tank in good condition, and a complete set of pattern plastics from bikerpartshop.com in the colour of your choice:
https://www.bikerpartshop.com/en/140-dtr-125-200
You can then store your valuable OEM plastics and either source another graphics kit the same as the one on the bike now or go your own way. One of the great things that makes the DTR such a usable classic is a good supply of brand new plastics, unlike all the other 90s 125cc trailies like the TS125R, KMX/KDX125 etc. where bodywaork is like hen's teeth. The only real difference between stock and pattern DTR panels is the leading edges of the rad shrouds are a slightly different shape but no-one but a card-carrying DTR trainspotter will ever notice this and it makes it easier to get out and enjoy the bike.
Glad you're enjoying the forum!
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POS mode on switch@Kristóf said in POS mode on switch:
So does this mean that with the main switch to ON and the lights switch to POS it should light up the auxiliary light even with the engine off?
No, lights switch to POS with the main switch to ON only illuminates the auxiliary light/tail light with the engine running because with the switches in these positions, the auxiliary and tail light receive an AC feed from the stator via the yellow/red wire.
@Kristóf said in POS mode on switch:
I'm asking this because my auxiliary light works when the main switch is to PARK but it doesn't work with the lights switch to POS
Yes, this is because with the main switch in the PARK position, the auxiliary and tail lights receive a DC feed directly from the battery via the red wire (which connects to blue/red at the main switch in PARK).
It took me a long time to fully understand this so glad I'm able to explain it properly!
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POS mode on switch@Kristóf You're correct about how the connections between wires are illustrated.
But, with the light switch (#23) in the "PO" or "ON" positions (PO = POS), yellow/red from the stator (main feed to the lights) changes to brown at the 3-pin connector, then at the light switch this connects to blue. The blue wire (which also branches off to the speedo/tacho illumination bulbs #32) then goes to the main switch (#24) where it connects to blue/red with the main switch in the "ON" position. Blue/red then goes to the auxiliary bulb (#26) and tail/brake light (#14) and so illuninates them.
It's confusing because the DT125R has AC lighting unlike a lot of bikes which run DC; look at the yellow/red wire coming from the stator (#7) and you'll see that after the 4-pin connector it splits into two. One side goes to the light switch (#23) and the other goes to the battery (#10) via the regulator/rectifier (#9) which changes the AC output from the stator into DC to charge the battery.
The DT125R is quite unique in this respect and one advantage of this setup is you can run a very high wattage headlamp bulb without flattening the battery. I always ran this one and even owners of bigger bikes were amazed how bright my headlamp was:
In fact looking again at the main switch #24 can make this easier to understand; when in the "Park" position, red from tha battery connects to blue/red, illuminating the auxiliary/tail lights with a direct DC supply from the battery.
Hope this helps! -
POS mode on switch@Kristóf Here's the 1989 to around 1998 3NC wiring diagram. As you can see with the lights turned to POS or On, at the headlamp switch yellow/red (main feed to the lights) connects to the blue wire for the front POS and rear light (yellow/red briefly becomes brown at the 3-pin connector just upstream of the light switch). This then connects to blue/red at the ingition switch and goes to the front POS and rear light so take a look at these wires and see if there's any abvious damage. Just before the ignition switch, blue also branches off to the speedo/tacho illumination bulbs so you could possibly learn more about exactly where the fault lies depending on if these light up at headlamp switch POS or ON.
I think this section of the wiring is also the same on bikes running the 3MB CDI unit even though the connectors from the loom to the CDI are different. Hope this helps!
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Carburetor help@Kristóf I'd be tempted to have a look on eBay etc for someone selling plastic washers of the correct inner/outer diameter. Either that or a hobby shop as these kinds of things are used a lot on radio-controlled models to make small adjustments. For example on a 1/10th scale RC car, placing a 2mm washer behind the rear wishbones is the equivalent of shortening the wheelbase 20mm in real life. For a fraction of the cost of one of those needle sets you could get a huge selection of different thicknesses and just see which ones fit the best. I'm not too familiar with the VM26SS carb but on the later flatslide carbs the plastic washers just keep the needle/circlip in place between the actual slide and the part the cable attaches to allowing a small amount of free movement, I'd just pick the washer thickness that does this best.
If you become (or already are) really good at jetting this could also open up other possibilities such as using one thick washer and one thin one and swapping them to move the needle the equivalent of half a clip position and that kind of thing. Maybe measure the distance between needle clip positions and base your selection on that when ordering?
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6k rpm limit@Rat80y The drain bolt stretching is a common thing on the DTR, IMO it's a design feature as if you overtighten it it usually snaps. Whilst being a right PITA to get the clutch cover off and wind out the broken part, it does mean the thread in the crankcase is saved (new crankcases = much more difficult/expensive than taking off an engine cover) so I hope you've ordered genuine from Fowlers (get a load of copper washers as well for future gearbox oil changes). Tightening torque is 15Nm so it's also well worth getting yourself a 1/4" drive torque wrench like this one:
https://planetx.co.uk/products/jobsworth-pro-torque-wrench-set-1
There is some truth in both your AI source and what your friend said. In the days of the 12bhp learner restriction, DTRs with the powervalve pinned shut would struggle to rev beyond 6k rpm but properly set up/derestricted/full power it should rev to around 10k.
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Noob@Rat80y I don't have a great deal of experience with the 2000 models with (usually) 5-wire servos etc. so what @calum said.
I'd definitely do a full carb clean including the emulsion tube (the brass tube the main jet screws into). A lot of people (including bike shops) miss this and don't realise it comes out because you have to screw the main jet back in without the brass washer and tap it gently to remove it from the carb body. The space between this and the carb body gets blocked with moisture, dirt etc and blocks more and more holes in the tube (which is how the air atomises the fuel) until it just starts fourstroking and won't rev out one day as this controls the mid-throttle fuelling. Just chucking it in an ultrasonic cleaner usually isn’t enough; you have to actually remove everything from the carb body, physically make sure all the jets and air passages are clear, then reassemble. Make sure the air supply to the emulsion tube is clear as well, it's the small brass tube on the right of the carb body just in front of the carb-to-airbox rubber. You should be able to blow through it, but only just.
Oh and BTW the float height on the flat slide TM28SS carb is 15.5-16.5mm despite what Haynes says, they got their TM28SS mixed up with the earlier VM26SS round slide carb whic was only on 1988 DTRs. Hope you get this sorted buddy.
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4FU and 32mm vs Slightly Ported Athena 170 and stock carb and 290 Jets@Karmona @calum @madgyver Interesting thread, as I've never run an Athena 170cc kit I can only agree with all the above comments.
One thing I would like to add though is you might like to consider a Tecno expansion chamber, possibly as well as the RH and DEP pipes. These are relatively inexpensive and from what I can see are basically an Athena pipe (which your above link recommends with the Athena 170 kit) with a clearcoat finish instead of black or chrome plating. A few years ago I ran one with a DEP silencer on an otherwise stock 1993 3NC French import and it made the power come in about 1000rpm earlier than stock with a sharp cutoff at about 9000rpm. I did some measuring of that pipe and a DEP I also had at the time and according to the A. Graham Bell two-stroke tuning book, all other things being unchanged, the Tecno delivers peak HP revs about 600rpm earlier than the DEP (basically my riding experience on the 125) whereas the DEP allows more overrev. So if you want a 170cc midrange monster for wheelies etc. it might just be the ticket, and it would be interesting if you could establish the correct jetting etc for all three pipes once you've built the engine.
Only thing I don't like about the Tecno is the clearcoat which bubbles up around the header pipe and is very difficult to remove. Eventually I managed it using rags soaked in paint thinner just wrapped around the pipe and left for a while (do this outdoors!) before wire brushing but I had to do this a few times to remove it all. I wish they wouldn't do this as it actually looks quite "factory" with the bare metal/welding heat marks:
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hello everyone@aragian Hi Bud and welcome to the Forum.
Sorry to hear your bike keeps killing CDI units, I owned a couple of 3NC DTRs and never had an issue but one of them, despite being an immaculate, low mileage example ran very badly when I got it and this was eventually traced to a pattern coil (among other things like incorrect jetting etc.). Those cheap pattern coils cause a lot of running problems on DTRs as they sometimes don't have the correct primary and secondary resistances, and in extreme cases this can damage the CDI so it's well worth taking a look at. Signs to look for (besides testing with a multimeter) include an overly long HT lead and being brightly coloured (OEM coils are black). If this is the case and you still have your original, best course of action is to replace the HT lead (explanation copied and pasted below):
Possibly could be the HT lead as they break own on DTRs causing this exact problem. The actual coil is very good quality so it's well worth fitting a new lead; you can cut off the very top of the coil's outer case where the lead pushes in with a junior hacksaw, pull out the old lead and solder the new one to the coil output for a really good connection. Then re-waterproof using Shoe Goo and electrical tape. Looks messy but no-one can see it under the tank, and you should notice a performance increase as the leads deteriorate over time. Much better option than just buying a new pattern coil as these often have different specs to OEM which can cause other issues. Fit a new NGK cap while you're there, try to get the type that's moulded into a single piece of rubber.
I had a high-rpm misfire once, after trying everything else we replaced the HT lead in the manner described above which took around 1 hour on a summer's day so the engine was neither stone cold nor up to operating temperature when I took it for a test ride. It wheelied out of the driveway without me even trying, and I couldn't believe how much better the performance was at all engine speeds. Made a big impression on me as I was 17 at the time and I'd spent practically a weekend trying to fix the bike and getting nowhere.I don't think any other DTR CDI unit can be fitted to a 3NC without serious alterations to or replacing the loom unfortunately (3MB CDIs are similar and appear to give a stronger spark than 3NCs but still have one or two different colour wires so I wouldn't advise it). In fact a company called The Tuning Works who import Zeeltronic ignitions into the UK once told me the stopped selling Zeeltronic CDIs for the DTR because Yamaha changed the electrical platform so many times in its 20+ year production run (although Zeeltronic will sell you one direct if you email them pictures of your existing CDI/loom connectors). I just had a quick Google and was pretty shocked at the 3NC CDI prices on eBay etc. but if it helps you this breaker in Germany appears to have two 3NC CDIs and a loom which might be worth having (it's a 3RM loom which I think = 3NC sold in Germany as the loom appears to have the correct connections for a 3NC CDI):
https://www.ebay.co.uk/itm/146868783391
https://www.ebay.co.uk/itm/157439162265
https://www.ebay.co.uk/itm/146948681784
There are specialists in the UK that mend CDI units, so if you have a few toasted OEM ones it might be worth looking into this by asking around local bike dealers etc.
As I say I don't have any experience of repeated CDI failures but it sounds like something is overloading it, either a pattern coil with resistances too high or something at the stator end. Early DTRs have strange electrical system where the same wire (yellow/red) powers the lights directly with AC (this gives the advantage of being able to run a 100/80W headlight bulb which a lot of bigger bikes can't do, see below) and charges the battery with DC via the regulator/rectifier. The stator has three coils; charging coil (battery), lighting coil and source coil which powers the the CDI (in fact four if you count the pulse coil on the outside of the flywheel which sends the CDI the signal every crank revolution like the crank sensor on a car). Haynes manual has all the numbers enabling you to test all these as well as the ignition coil so it's well worth getting yourself a flywheel puller and a multimeter and going through this; it could be as simple as getting another 3NC stator and bolting it on (Yamaha used to sell the stator coils separately but they're hard to find now and IIRC you have to solder them up yourself).
Understand the attraction of getting a modern 450 but these aren't without their own problems; a lot of people in the MX/Enduro world are utterly fed up with the "four stroke revolution" as they can be complicated and expensive to fix when they blow up. If you persevere with this reach a definitive conclusion/remedy your DTR will be reliable and easy to keep that way for the forseeable future, a usable classic with advantages such as VERY powerful headlight, Autolube (literally mechanical engine management from the 1970s), limitless brand new plastics from Portugal and ease of maintenance due to grease nipples everywhere etc.
Here's a 3NC wiring diagram if you don't already have it, hope this helps:
100/80W Headlight Bulb Explanation:
The stock DTR headlight takes a P45T bulb (similar fitting to H4 but not the same) and has AC lighting (i.e the power for the lights comes straight from the magneto without involving the battery) so you can run a 100/80W halogen bulb without flattening the battery unlike a lot of bigger bikes which run DC. The DTR’s actual light lens/reflector is the same as all Yamaha superbikes of the 80s like the RD500LC and XJ900, but Yamaha cheaped out and fitted a 45/40W candle to the DTR which is why lots of people don’t find it bright enough. 100/80W bulb lights up the roads/trails like a rally car and retains an MOT-friendly beam pattern. Once a year or two ago I met up with a bunch of guys greenlaning on modern KTMs and decided to tag along with them as it was getting dark; they couldn’t believe how much brighter my headlight was. Get this one:
Also MOT stations have a headlight beam board and can set up the headlight perfectly for you in a few minutes but you can get it more or less where it should be by finding a brick wall and measuring the height the centre of the headlight glass comes up to with you sat on the bike. Then sit on the bike about 6 feet from the wall and get the headlight main beam to this level and pointing straight ahead using the adjusters.
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Yamaha Dt200 Swingarm to Dt125@YzDt85 If you mean the DT200R 3ET alloy swingarm, as far as I know it's the same overall length and uses the same pivot/linkage bearings as the DT125R steel arm (and takes the same All Balls 28-1212 pivot bearing kit). Here are some pics of a bench mock-up I did a couple of years ago using DT125R crankcases and rear hub mated to 3ET alloy swingarm, rear wheel spacers and caliper hanger. As you can see the 428 sprockets lined up quite well (I also had to use a 3mm thick M20 washer between the caliper hanger and swingarm to get it as good as it could possibly be with the items I had to hand).
IMO the engine boss at the rear of the crankcases dictates sprocket alignment probably more than the frame, and I reasoned if the sprockets aligned with the original hub the wheels are probably in alignment as well (although having no roadworthy DT125R at the time meant I had no way to check this).
Don't forget the all-important swingarm side clearance, it's a lot easier than Yamaha makes it look and if you get this right you can get the arm to fall under it's own weight with <1mm side-to-side play which massively improves suspension compliance and chain/sprocket wear:
Top DT200R tip; the plastic mud flap that protects the rear shock wears the (basically priceless) alloy swingarm away at the rear of the linkage bearing over time so it can be helpful to install something to prevent this. A lot of people with modern Huskies, KTMs etc. JB Weld a coin to the surface of the arm as they're prone to it as well.
I considered all that mud and chain lube floating about to be quite a harsh environment in which to try and glue two pieces of metal together so on my 250EXC I used the plastic sleeve which you get inside one of those boxes of sticky labels they sell in the Post Office cut open and cable tied on.
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The Aphrodite Project (Cagiva Planet 125 RD 350 YPVS 421 Conversion)@Calum This is an amazing project, looking forward to the next instalment!
It's crazy how Yamaha making the 350 Banshee has breathed new life into the 350LC/YPVS community. This might be of interest, over on 999Lazer YouTube channel they're covering an auction of someone's entire collection which includes a brand new Banshee still in the crate: https://www.youtube.com/watch?v=E_mb4AUi4kg
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Merry Christmas 2025Merry Christmas everyone!
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‘89 DTRE NO SPARK!!@Calum @raceraidan Interesting thread.
I once owned a 1998 DT125RE French import which looked identical to a DT125R the same year (pic 1). It had a larger battery and separate toolikt compartment as well as the electric start wiring.
During this time I was fortunate enough to source a Yamaha service manual for this exact model, I still have this and here are some pictures of the wiring diagram. I believe KTM also used this engine/electrical platform for the LC2 125 which they sold a lot of in Germany (I bought 2 or 3 3MB CDI units marked LC2 125 from German breakers, and also some NIP 3MB YPVS servos which had both the Yamaha and KTM part numbers on the packaging (sadly now all sold). During my ownership I tried all these items on the bike and they all just plugged into the loom (same connectors) and worked. I'm pretty certain the (inverted) flywheel and stator were both stamped 3MB.
As you can see this model also has a clutch switch which IIRC, with the clutch pulled in, allows you to start the engine in gear even with the sidestand down, but cuts the ignition when you let out the clutch to try and pull away. If you've already looked at the sidestand switch I'd locate this and give it a dose of WD40 etc. as a starting point. Also the two relays (items 12 and 13) are worth a look although I'm not sure how you'd go about testing these.
It might be of some help to just get some more and plug them in and try them. Here's a link to the KTM parts fiche; search Google/eBay etc. for the KTM part numbers as well as Yamaha France and you might get lucky with a European breaker as they can be quite diligent with posting up used parts for sale including the original numbers:
https://www.trevorpopemotorcycles.co.uk/index.php?main_page=ktm_fiche_finder
Here are some pics of the wiring diagram, not sure if the Gilera SC125 used the same electrical platform but hope this helps:
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HELP with Supermoto to Dirt wheels on DT125R SM... questions about hubs etc.@ChuckSR86 I think the easiest way of doing this would be to just obtain a complete DTR or DTRe front end, rear wheel (and possibly swingarm/rear brake assembly) and shock. All these items are fairly common on eBay etc and are easier to swap out than you might think (I once had to replace a DTR swingarm when I'd arranged to go out riding the next day and got a spare one I had fitted in an evening, including the all-important swingarm side clearance).
Regarding the shock, I've heard some people say the DTX shock is shorter than the DTR/DTRe, I'm not sure about this but I once bought a few "DTR" shocks from a breaker which included one a few mm shorter than all the others but otherwise identical (maybe @calum or another DTX owner can confirm this?).
Running DTR forks mean you'll get to use fork gaiters which massively increase seal life off-road, and the whole operation will be a lot easier than getting into one-off bespoke front end conversions etc. which can be a bit of a nightmare when it comes to stuff like sorting a speedo drive and maintaining forks where the seller might have been a bit economical with the truth regarding what year of bike they came from.
Never owned or worked on a DTX so can anyone confirm if this is indeed straightforward?
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Suspension setup for a heavier rider.@Calum Yes @SpookDog runs the Hyperpro fork springs IIRC and is happy with them.
I weigh around 150lbs and to make my '98 DTR a bit better off-road, my suspension setup was:
YSS adjustable rear shock and Lust Racing 25mm jack-up kit (the YSS shock is slightly shorter than OEM and the Lust Racing kit corrects this).
XT600 3AJ fork springs (20% stiffer than stock) and 15W oil (stock is 10W); this is a well-known DTR upgrade for greenlaning etc. and helps the bike jump better and resist bottoming. I adjusted the spring preload/rebound on the YSS shock to suit and the bike jumped better than the 2020 KTM 250EXC I also owned at the time.
I've also heard of people swapping on an XT600E rear shock spring, this apparently sorts the spring rate but the stock DTR shock has no damping adjustment so you might end up with the rear being a bit of a pogo stick (I was running the YSS rebound on position 29 out of 30).
The correct way to set up suspension according to a lot of racers is get the correct spring rate first; this is achieved by aiming for 25% static sag (the amount the suspension compresses when you sit on the stationary bike wearing all your usual riding gear, helmet etc.). If you fall down the hole of just adding heavier and heavier fork oil it will make the front end feel mushy and unresponsive. Once you've got the right spring rate, then is the time to start working on damping which is a little more subjective as it depends on where you ride, how fast you go, how you like it to feel etc.
I've made this sound a lot more difficult then it is TBH, the spring rate is something you can do without even riding the bike to get a starting point (good project for a wet day), then a few ride-and-feel sessions and you'll be well on your way. Getting this right can make the bike feel like it really belongs to you and is worth spending time on.
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Ideas on tunningThe best place to get a Zeeltronic ignition is direct from the manufacturer, they ask you to send pictures of your connectors so they can custom make one that plugs straight into the CDI connectors on your wiring loom.
I installed one on my '93 4BL with 3NC electrics and by taking power for the CDI from the brown wire (main feed on Yamahas) on the 3-wire servo connector and running a 5-wire servo, it's possible to install it without altering the main loom at all meaning you can revert back to the 3NC CDI/3-wire servo stock setup easily.
Zeeltronic are very helpful and free with advice when you purchase a unit from them as well.