Yamaha DT125R '01 - Running Project

  • Well. I sometimes wonder why I bother. If you have ever ridden a proper Off-road motorcycle, you quickly realise when thraping a DT, just what a sqeegey, pogo stick, slightly too small, floppy forked, 80s steel timer chassis it really is. When it comes to modifying a DT. You might aswell buy something better. But anyway, I like playing with it so..

    Fitted a 1/4 Action throttle from a 1988 KX80. The throttle tube is a larger diameter, much more comfortable and has been invaluable as an upgrade. I had to modify my 'Genuine' throttle cable by cutting back a bit of outer sheath. XT600 brake lever is a great swap, and I use a little shorty alloy clutch lever of a 85cc on there.

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    Needed to replace the original headlight cluster.

    Missed out on a decent Yamaha WR400 headlight.(Perfect shape) Got one of a Aprilia RX, had to do some wiring for this. Needed to be painted white of course. Its worse than the DT headlight.. but, got the look.

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    If your into DTRs. Then the DT200R (3ET) is the one to have. I couldn't find much information on these (YZ) wheel upgrades I've seen. I wanted alloy wheels on it like the 200. So after some research and a failed attempt at getting a set of WR200 wheels, I concluded that 1988-94 Yamaha YZ wheels have the same size rear hub as the DT. Straight swap. For the front, had to be 1987'-1988' because they ran similar sized rotors back then. However the hubs are about 10mm wider on the YZ, So I chose some YZ 1986' front spacers, looked similar proportion to match a DT fork in the pictures. If your going to swap to a YZ wheel, I gave up trying to fit the Speedo drive back on and took it off. Took of the clocks. Then fitted a bicycle wired speedo, just for an MOT really.. its crap and does not register the pick up past 60 mph or so. Minor price to pay. A vapour unit out of the budget. Don't need idiot lights for wheelies.

    Yamaha built the 1986-1988 YZs with Gold anodised rims and man.. wish I could find a back one. The front is a 1988- the back of a 1994. MX was starting to use 19" rear wheels for better drive and handling back in the early 90s. Yamaha were on this on the YZ range. Bigger wheel does throw the gearing off slightly on acceleration. Got a big dutty knobbly on the back and you really loose out on power if you have to nip along the road.

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    The rear shock is crap on any DTR, or at least mine was. Did some googling' and a man in Australia agreed with me, and I had to copy his idea for myself. The DT uses the same shock to linkage fixing as 87-88' YZs Shipped a 1987' Yamaha YZ490 Rear shocker that bolts right in! Its even got Yamaha's 'B.A.S.S' system on it. Which is rubbish.. but cool anyway. When fitting it, the top damper mount on a YZ frame is different, apparently much narrower than the DT frame, so you will need to use the bearing with it's fixed spacer off the DT shock and replace the YZ one with it. I actually used two big cable ties instead just to stop any lateral movement under compression. Anyway I now have Adjustable spring rate, Damping settings and Rebound settings. It will sit pretty high on a firm setting. 4-5cm lift. I also stuck with my short Dog-bones,3cm riser ones. It gives the shock better clearance from the swing arm, its a tight fit.

    I cannot find the thread any more, but here are the pictures on the suspension modifications

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    I already replaced the battery with a capacitor from '2strokeracelab' - check it out. The shock is bigger than the DT unit, longer and a fatter spring with of course,with a piggyback reservoir. So there is no room for the battery. It is also no going back as there is the tab which the battery tray is bolted to on the frame, which has to be cut off for the shock to be accepted properly. I also cut the side cover apart. Bit easier to get a flat head in for adjustment and gives me access to the Yamy Tool kit.

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    I use 15w Fork oil and it makes the best of the standard forks. I do own a very nice set of 1991' WR200 Kayaba Forks. I chose them because the WR yoke had an Ignition mount. They are just the right forks for it. But I don't want to modify the frame to accept the WR stem. I'm looking at having the Stem pressed from the WR yoke, and getting it machined down with an extended thread which would allow me to just use the original top cap and ball bearing race on the DT. Need to model it in 3D first.

    I'm at University currently so I just stock pile things at the moment. But future updates; Installing a Twin radiator configuration from the DT200R(3ET) - Got all the goodies now. I've also got a 'Ignitech DCCDPI2' on the way. The 3RM' really needs ignition modification before anything else. And the fiendishly unfriendly, how do I horse anything bigger than a 30mm Carburettor? plans to Original Air box configuration at some point,

    It does not need to be big, I have drilled out the Air box already with good results with some Jetting and Pipecross Airfilter fitted. But I do have a Keihin PWK 36 that would be alot of fun.

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    Picked up a very nice Yamaha TZR125RR (3MB00-P-Y2) Barrel ages ago. (The real deal Y3 Belgarda' has eluded me) Just a display piece at the moment. Interested to hear about any Porting experiences.


  • We Bother Because We Can!

    Hi Welcome!

    That's an impressive build you've got going on there. It's nice to see people not shy away from custom work done to their DT's.

    To give them credit they are fun in their stock form. I remember going from my bike to a friends stock DTR and thinking wow my upgrades are really just that! Upgrades. From brakes, to suspension to engine work my bike has seen it all. And despite all that, I actually found the pogo stick form more fun to ride. It was a sense of adventure. I digress.

    Some interesting points you may like to hear.

    The Yamaha DT230 Lanza featured here:


    Its latest incarnation sports fron and back alloy wheels, which are a direct fitment to our bikes.
    It also sports an Aluminium swing arm, again direct replacement.
    And finally it sports an uprated suspension shock. I don't know if this is a direct replacement but I can't see it being far off.

    Note the extra tank down by the generator.

    Also there are better options than pressing stems out my friend.

    If you want better forks then there are lots of options out there.

    From thicker oil, to progressive springs.


    Or if you are feeling adventurous, I describe a way it can be done that requires no butchering of your bike. In fact you create an extension to the from which allows you to embed a thicker stem and bearing into it. Have a look in the tutorials or my build thread.

    Seeing as you don't shy away from bespoke I think you might be interested in that last one.

    As for tuning, there isn't a lot my DT hasn't seen.

    I was running a TZR125 R Belgarda 4DL Engine in my dt

    It was running a ported 3MB00P engine, porting was nice but the barrel is really no different from the normal 3MB00. As you say it is the TZR125RR Barrel that is the holy grail. A barrel that was actually made by Polini for Yamaha. Interesting stuff.

    Out of everything I have done to my bike mate, the best thing you can do for the money. Is buy yourself a zeeltronic ignition system. I am telling you now, don't waste your money on porting, carbs etc until you have one. As there isn't anything else out there that compares to those units.

    They don't give you more peak BHP but rather more BHP through the rev range. And also of course, the ability to raise the red line to 20'000 rpm. But youi will of course require forged internals. Something I ran on both my TZR lump and DTR lump.

    As for carbs, I ran a VHSA32mm Dellorto, these can be found on the TZR's. But the one you have looks lovely.

    Bigger is not always better with Two strokes. If you're interested, then go out and read/buy Graham Bell's Two Stroke Performance Tuning. Absolute joy to read and you really do learn a lot.

    Keep us posted with the build. Looks like a goodun. And be sure to post up any questions you may have in the relevant sections.

    We're just in the process of migrating from our old forum, so information is pretty sparse. Feel free to add interesting facts which are missing,



  • Hi, Thank you.

    Yeah.. a Zeely would be nice to be honest.

    I have followed your project for a while and it is very impressive, I have had my DT for a couple of years now. And yeah completely stock (De-restricted) of course, has been the best performance so far. And to answer the question of the Pre -94' CDI vs Later years 99' on bikes. Well. It's pretty close between them haha. Good times.

    A little note, the older 3 wire DT's have a much more raw engine noise on tick over. Yamaha redesigned the stator motor with much else after 99'. Older models really have the right engine noise. Exhaust noise very much the same for all models on a DEP though, no missing out.

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    Jeez. You should see the state of it now 7,000 miles later. I rode it hard. It is need of a full restoration. Mechanically supreme however. The fit and finish is the last thing I can be bothered with.

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    Hard hit.

    Yes. The Lanza. I've seen only ever seen about 3 or 4 on eVil bay. They were never really imported here much by anyone it looks like. I know Yamaha never sold em in the UK- like the DT200R(3ET). I could never find any parts. I am considering a DT200R Alloy swinger - from Australia.. That is the easiest weight saving option out there I think. But not sure. I want the wheel base to be a bit longer on it really, so an extra 2" of YZ alloy or WR and fettling time seems a more pleasing upgrade, but where do you stop. I cant make my mind up.

    Yeah still got my eyes on any TDR - TZRR stuff at the moment. It is getting the bigger inlet that would be a score for me.

    Anyway, I'll keep from talking about it and get some updates up here. I'll see if there is anything useful I know.

    Quickly as well, do you rate Mick Abbey tuning? Your barrel looked good but I don't want to rework anything.

    Thanks for the links.

  • It won't be the ignition causing engine noise. The later dtrs have catalytics in the exhaust pipe. Amongst other restrictions. Also if you are not runng powervalve systems then it will sound much more raw on tick over.

    What can I say, the dtr was never meant to be a born racer. Yeah Mick Abbeys work is good. But it will only be as good as the rest of the tuning work to be honest.

    Yes, but be careful as not all lanzas have alloy arms. There is one in Japan at the moment for sale for only a few quid. Cheap upgrade if yoh ask me.

  • I saw some DTX Excels on the ol interweb with tread, and I thought. Now is the time. I'll build a street machine.

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    I got bored of trying to compile good condition early 90s YZ parts. It was then that I remembered a WR200 Swingarm and Caliper set that I found. Decided to go with it and fit it to my YZ shock.

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    Started with a proof of concept and fitted it together. Looks good, and the alloy swingarm frees up the rear. Got the weight down to under 110kg. It feels nice. Bust all the 4stroke 125s to pieces and keep up with the Aprilia boys.

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    Yeah the WR200 swingarm fits rather well. Straight in. I was concerned that the bigger swingarm would hit the reservoir on the shock under compression, but I've got clearance due the ride height. However the linkage frame bolt on my bike has fused absolute into the frame. So Im using the original DT suspension links onto the WR swingarm. Works fine, but using the the DT dog bones (original set), they are too short and basically jack the bike up about 6cm. This and the taller YZ unit make it ridiculous. The problem with this is reducing the steering angle. It's about 19 degrees or so now, and I can imagine, I'm pretty sure this will be a twitchy mess at speed. Lowering after-market links for the DT are stupid money. So I'll make some.

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    I need to sort out that spacer.

    Wound the spring rate right up to compensate, makes the ride a little too plush for the road. It will do for now. Quick note. To adjust the spring rate when fitting this to a DT. There is NO access without removing the Side panels, Seat, Battery tray and Airbox. Ballache.

    Next UP. Twin Rads. Because Twin Rads are cool. That and, I've removed the Oil pump and tank, so there is a big useless gap that needs to be filled. Why not unite a Radiator to its spritual home?

    Fitted it with a couple of bolts into the OEM threaded tabs on the DT200R Right hand radiator. It's very snug. The plumbing is right up against the tank in situe, With the plumbing hooked up it's a rigid fit, Brackets one day. I did plan to mount the Bigger offside DT200 Rad I've got but I couldn't seat it in there without some fabrication. So now I have two header tanks. Looks strange.

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    Managed to get the all important DT200R split pipe.

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    Forgot about the spindle. DT spindle is too long, The WR swinger is narrower and you will need WR spacers and caliper. Quite like the Nissin unit of the WR, think it should give much more bite, and its lighter too. Got the lot pretty cheap.

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    Onto stuffing the new carb in there.

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    Using a 1989 Yamaha YZ125 inlet, they are actually for a TM34, 35.36 inlets came later into the early 90s. Which I forgot. So I filed some material away for the PWK36.

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    It was not going to fit, so I used a spacer template to relocate the fixings onto the Reed block. Also sanded and smoothed the bore of the inlet to match the DT reed block area. No steps or intrusions is a must.

    Snug. Using a early 90s KX throttle cable, Running the same carb and Throttle housing as those KXs now. Werid setup.
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    Had a bit of trouble clearing the frame and shock to fit a Air filter. The Ram Air filter tucks into the air box a little, keeps some chain crap of it. Never going to be any good in the wet.

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    Had a screw head that was completely chewed. Don't be a clot. I'll never use it again.

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    Was not sure what to do with a caliper set up. Looked at TZRR units, TDR, XT and even a Cagiva Mito brembo. Nearly bought a Yamaha YZ Nissin unit, which would of probably been a better performer, Settled on a YZF125 caliper because its the same unit on the DTX. Cheap, and gold..ish should be alright.

    Made a template out of wood to hang it.

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    Got some old, and very soft 6mm Aluminium and made the bracket by hand,

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    Cut some 15mm spacers to hang the caliper.

    I didn't check the specific CDI on it, Mines a (3RM-20).. Bugger. went ahead and ordered a 3RM-00 CDI, for a loom which is slightly different and uses different connectors, So its got to go back to Ignitech and be sorted. My fault. So I cant play with the Ignitech for a while.

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    Damn. Postage isn't too bad. 8euro to sort.

    Once that lot is in, think its prime time to sort out that old 3MB00 P barrel.

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    There is a bit of surface rust in there, but it is in reasonable condition. It looks like the piston seized in there a long time ago. Needs a re-bore.

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  • Don't know what you are doing with your images lol. You just need to paste the image location that is all. So www.someaddress.com/yourpicture.extension should do the trick.

    Looking very good. Like what you have done so far. But be very cautious about that front brake bracket! That could be disastrous if it's too soft.

    Also I found when going from single pot to four pot calipers Thag I needed a bigger master cylinder. So just keep your eye on that one.

    Nice carb you got there. Shame about the damage but not the end of the world.

    The wheels look good and the swing arm looks very epic. Not sure about keeping up with Aprilias but sure give it a go!

    Nice build though. It is what we like to see!

  • @Calum Yeah, Not sure what is going on with it, I copy the embed link but still get all the text? Not happend before. But it works no other way on here, Werid. Problem my end.

    Tis quite soft ally, but 6mm plate should suffice any deformation. It's a strong bracket. I would prefer to watercut and plate some steel.

    As for keeping up with the Aprilia boys, well.Impossible on any open' road true! I will own a Rotax 122 one day. Nearly got a 1996 Aprilia RX125. Fantastic engines that CAN indeed be very reliable much too everybody's misconception of them. Although holding them at 12k all Sunday is the addictive demise of thy road 2stroke. Expensive past times.

    But yeah cheers dude.

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    No 8,500 Rpm Will not suffice. (Picture Illustrates nothing usefull) Just browsing.

    Had a little peak at the Ignitech Software and Manual. Love this stuff. Pretty unnecessary for this project but it gives some good performance options. (The main reason I bought this was too eliminate the Factory CDI ignition retardation.) It's not necessary but increasing the Max Rev Range is important for any gains in gearing at this point. Also advancing the timing is a very easy performance gain. If you do this Beware of using lower octane fuel. Pretty noticeable.

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    Bike was sweating in the shed. The plating and steel are so thin on these DT125R Dep's. I hate them. Bad build quality for the money, but indeed the best pipe for it all rounder wise. Mines starting to blow holes.


    Electrolysis is a process by which Ferric Oxide (Pesky rust...) is turned back into Iron. Had De-Rusting tank set up already. I was worried it would attack the chrome slightly but it is absolutely fine.

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    'Function over form' and silver exhaust paint is applied. Ah well. the Chrome had excellent heat distortion and looked well worked in loveely purpley Gold. But it is an expendable right? Best try and keep it from disitergrating. Think I will try and wrap it in Ceramic Fibre cloth, Keep it covered.

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    The inlet and Carburetor just is not where I want it to be. Needs to sit in there as Factory as it can be. I've made a template out of card using a Reed Spacer as a base template. Definitely going to have to make a Inlet. I fabricate it, but damn, I'm not doing Tig anytime soon, Great. Got some time to kill anyway.

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    Could print one? Haha will delve into that soon.

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    The wheel base has increased some 100mm. Same length as a WR200 and 20mm longer than a same era YZ. Success. Got some FZR400 Tie bars which are 150mm. perfect lowering height, but not the same thickness steel and are plastic coated not plated? Had too drill them out to 16mm to accept the DT's chunkier linkage bolts. Cheap fix. Not recommended.

    Any help please with a chain. I cannot find a 428 Heavy Duty Drive chain that is long enough.. like anywhere. Probably will go 520 and Sprockets because I've got a spare. But a 428 would be bang on and standard.

  • Got digging around the ol' interweb and quickly realised the Radiators I received were indeed. WR200 units..This explains why my plan never worked as I hoped. Ohh well it's close enough,

    DT200R Right H
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    WR200 Right H

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    Unrelated note, Saw this wicked early 90s DT-RD350/TZR Supermoto ages ago on the net. Found it again recently. Got me thinking about all the great projects I have seen.

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    MOT coming February, Fork conversion towards Easter. Not ridden the ol girl in vein for too long.

  • You don't need the embedded link. Just the image location with no fancy embed stuff.

    Comming along nicely. Yeah I thought that about the dep pipe too. I ditched my pipe in the end. Disgusted by the poor quality metal. Good performance gains though.

    Yeah I was jawing over that rd project for a long time haha!

    As far as the cdi is concerned. Bang for buck it's the best modification and I have done the lot.

    Good luck with the mot keep us posted.

  • Nice thread you got going looking good so far keep it up 👍

  • Decided against using the Kehin 36. Effort. it's not going to give me the right results. Went shopping, but I could not find anything suitable accept for a couple of Dell'orto VH34s or old TMX34's for reasonable price. Don't need anything bigger right now.

    Got this Mikuni TM32 which desperately needs a clean and polish. And a float bowl. It's been mangled.

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    Who needs a digital display?

    Got this TZR Tachometer. Love the dial, goes to 12k. Yamaha part, perfect. You can always feel what the engine is doing, but it's nice to see what's going on. Not too useful, and it's rather big, but a single clock up front, clean, simple on the WR yoke.

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    I prefer the Mikuni TM series + this version has the Fuel inlet on the right side. Wont bother with using the Airbox.

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  • So, gave up on the MOT. All because of a couple of Mikuni Pilot Jets. Postage took too long, could not finish it up.

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    Jetting for an Open Air filter is a pain in the rear. Factory settings don't really apply and she's leaner than I anticipated. Which is kind of fun in a boring way. Jetting is the cheapest power you can buy! Best get it right.

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    Dep header is swiss cheese so I wrapped it for now using Titanium fibre exhaust wrap. Operating temperature for the expansion pipe should be better? Hotter pipe to help control the temperature of exhaust gases. New pipe has to wait. Ah well. it's a Student build.

    Don't ever use that GumGum tape, pastey shite. Just awful on a header pipe.

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    May have got impatient and dremel'd out the standard Inlet manifold. Pluged over the Oil injection entry and smoothed out and increased the bore size internally and opened the flange 28-32mm.

    Good thing about the standard manifold is the YIES boost bottle. Adds some much needed refinement to the 2 stroke.

    Increasing the bore I had to trim the bottom of the YIES snout as it protrudes further into the bore and will potentially disrupt airflow.

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    The air filter and carb only just fits in and its bent around the YZ shocker. So tight and a bitch to get in and out.

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    Running 520 YZ125 AFAM chain 13T drive sprocket and Talon 51T rear. Makes it perky. She sounds like a beast with and without the airbox amplifying it.

  • @Darty haha nice one!

  • I'm liking it!

  • Nice work there, liking the fabrication. I have often thought about a dt200r or wr200 swingarm but I spent ages getting the old bearings out of mine and powdercoating it so I left it. So it was a perfect fit you say? Except the dog bones.

    Fitting a different carburetor was also a nightmare, especially on a divided throttle cable (I'm running auto lube on my 200cx conversion) I had a tm32 flat side which was very tricky to fit because it isn't angle on the spigots. If you carb isn't level enough it can mess with the floats. I then ran a tmx30 carburetor very similar to the wr200s tm30ss carburetor which ran very nicely and few modifications. And I am currently running a tm34ss which has angled spigots. Which I'd recommend 🙂

  • Ah cheers boys, @Calum @ConnorDTR there is still so much I need to do. Not enough time!

    @Louis-James Yeah, pretty much a perfect fit. I had to turn a spacer on the sprocket side of the swingarm because there is a gap between the bearing end cap and the crankcase, WR200 crankcase must have a wider section across the swingarm bolt.

    Fits fine without it, but needs the spacer for the correct lateral torque. But it's a bolt in job and I really recommend it.

    Definitely get yourself the WR200 linkage set (Alloy) I need to fit mine then you can potentially run very nice rear dampers from a newer generation. Got a nice TM Ohlins shock, looks to fit.

    The TM32 isn't a great fit, I've not run it for long, but it's possible it's already disrupting the floats. But fit for purpose just. Not ideal. Just had a look at some TM34Ss and yeah man, that looks to be a much better idea actually.

    Ultimately I think you have got too make a Inlet manifold, I can't fit anything else past the shock without one.

  • Spring has crept around ol' Coventry today. Blessed. And then some bits finally turned up at lunch time.

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    Most of Yamaha's road going production castings are begging to be cleaned up gone over properly, because the castings make you wince in places. They are cost effective without hand finishing and, of course the time and labour is not necessary for a production run. Not even because it's old, they need some love.
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    Wrekt...She's a bit of a lemon. Cracked the sleeve to the top above the exhaust port. Still, new sleeve and some light repair work around the port and she's good to go. This will be the test mule for running a larger bore.

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    Ignitech came through, I should of spec'd a longer loom so I could fit it into the now empty airbox. There isn't much of anywhere with decent access and tucked in.

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    Looking forward to building up a 200R block.. maaybe some time on that.

    Anyone want some money for a WR200 powervalve they somehow don't need? I'm your man.

  • So what's the difference with the ignitech CDI and the Zeeltronic? Only just heard of the ignitechs

  • Very smart. Nice auxiliary exhaust ports on them too! Should be a beast.

    Powervalves are tricky things to come by. I askrd about having one made but they simply wouldn't do it because of cost!

    Very frustrating but I am sure you will find one one day!

    Easy on how you remove that sleeve. Even companies have been known to damage the ally cylinder removing them.

    Will.keep an eye out for updates.

  • You can buy new sleeves on eBay, I saw some wiseco ones a few years back. I have the nickasil bore, not sure what models had what