Yamaha DT125R '01 - Running Project



  • A Custom ignition, either or, will be a dramatic improvement. Shouldn't be any difference.



  • Some little bits.

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    Removing material to clear the flanged nut I'm using off the fork leg for the correct position. Renewed this bit a while ago, the YZF carrier is not the best idea.

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    Finished setup for now, Lathed up 16mm Brass spacers and fitted together with 10.4 HT bolts.

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    98' YZ 250 1/4 throttle with billet alloy throttle tube, is plush like em snappy

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    New ceramic resistor.

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    Trying to keep Jap with a Denso W27ES-U plug. £1.70!

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    Call me the 'Artful bodger' Ran into some issues just using a capacitor to run the Ignitech. So strapped in ol' faithful in what's left of the only space available on the bike.

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    Slowly rebuilding my TM32. Sanded, wet sanded and polished internals.

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    Satisfied like glass. Giving a helping hand to the inevitable ingress of dirt to be combusted.

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    Remounting the WR rad, cutting the thermostat housing down, deleting the oil tank cap fixture from the support and shortening the rear radiator outlet futher to clear the tank. Then moving the whole thing forward to sit flush and safe.

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    Having alot of fun tearing it about, led me to ignore a serious issue. After letting the chain eat my original WR200 chain guide and very good condition Delta-box swinger, it was time to go back and fit plan A.
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    Drilled and M6 taped new mounts. Didn't feel like sacrilege after fucking it over already.

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    I wanted to do this for ages, fitting a YZ/WR 98'-02' chain guide looked to fit in my head. Can now replace it without having to take the swinger off, and readily available to replace now, as WR200 and early YZ 1990-94' sliders are rare, or silly money new.

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    Ugraded to RFX slider in blue, made from a hard polypropylene instead of silicone rubber. Should do the trick.

    Running the airbox door removed and older 3MB airbox tract now with a 450 Main jet can you believe. It's now absolutely perfect with peak power dropping away at about 10,900rpm. She sings. Ready for my new ported top end. Looking to go full road racer at 12,600rpm with the larger carb.
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    Shortened the chain, back on a Steel sprocket with a 45T 520, good for 80 again which was missed,

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    I always preferred the original clutch cases, got a nice oil pump housing design. Had to use my 4DL one.

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    Standard (left) vs EBC's heavy duty clutch spring. Good upgrade, firm clutch with a quicker release.
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    New EBC clutch plates a while back had trashed my gearbox oil, found this, cause race bike..

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    Threaded insert and bolt for oil pump delete, re-sharpened foot pegs and brake pedal from the trail bike days.



  • @Darty Yes mate that's looking the tits!

    Keep the updates rolling.



  • @Calum Cheers yo, got some real nice goodies coming soon!



  • Excellent work @Darty !! Good to see you doing more work to this beast.. Kinda worried now incase my chains been eating into my wr swing arm i will need to check tomorrow I've just been using the DTR chain slider on the wr swing arm hope its all good as I've been using the bike 24/7 lol.. Don't fancy getting rid of the capacitator by any chance now your using a battery again!? My capacitator is lost in the woods somewhere obviously wasn't secured enough 😆



  • @Biker_123 I've been using mine to get to work everyday, such a laugh I had it jacked up to high, like a 93cm seat height through the chain geometry out, swing-arm was too big for front sprocket clearance it's alright otherwise.

    shit man, get it bolted it under the seat xD I definitely got to hang on to my racing Capacitor, it was hand made from Greece



  • @Darty No problem haha had me worried about my swingarm for a bit there 😆.. I'll need to pick up another capacitator my local motorbike shop does them but needs to order them in so takes a while! Oh for sure it'll be getting secured better this time round 🙂



  • Yamaha DT230 Lanza - Air Duct (4TP-14437-00)

    Came all the way from Japan.

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    Keeping a controlled Air flow. Jetted, It works well with the 125R, highly recommended. All 170cc Kits should come with a larger duct.

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    Non existent Mikuni gaskets for TM32-34. So I made my own body gaskets.

    Built a TM34 aswell to try in the future.

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    Full rebuild. A TM32 and 34 have the same bodys so I can tune with both without another custom inlet for now.

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    hmmm. Got one of my 3MB-P-00 barrels transfers cleaned and Ports re-worked and polished.

    Off to get it Ported to a Top end tune, and having my 4DL P' cylinder head and Powervalve fettled with it.

    Full chassis rebuild and paint, so maybe by next Summer, she's done. Maybe...



  • Looks.like some healthy upgrades now. Should free up a pony or two that's for sure!



  • The sooner it goes back together, the sooner it can be destroyed, that is what it's all about.

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    It just doesn't fit anymore, and fried the wadding in 3 weeks.

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    RIP. DEP system.

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    The worst thing is having a Taxed and Insured Motorcycle that looks like this. Chassis needs work.

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    I can also illustrate the knarly fucking dent to the frame rail I found a few years ago.

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    WTF... How do you even?

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    That impact has twisted the down tube, its almost imperceptible, but the engine mounts tell me it's all been effected. I have seen worse before though, much worse! So still a really good base to build on.

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    Off comes the old barrel, honing marks are still there.

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    It ran perfect all of it's life. I ruined the mixture towards the end. The Powervalve was completely coked up. If you maintain these things they will see 14,000 miles on a set of rings.
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    It did heat seize once, didn't last long and never had any-more trouble.

    Found an unused WR400 headlight. What a score. Always fancied one.

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    Single bulb Enduro unit, so nothing special really.

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    WR vs RX, Not sure what I like more.
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    I found a good solution, 1987 YZ125 airboot.

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    Ready for a 34mm housing, so no more pod-filters, which are rubbish.

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    Ducati Brembo 4 pot caliper and Radial Master cylinder. Using a XT660X 320mm brake disc of my DTX hub, I will be able to sling the 4pot in there.

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    KPmotosolutions did a nice job. Ported, Port timings revised, Squish revised, crown re-machined, and powervalve revised. Tis a little beast.

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    All out for top end, It's a 134cc race tuned still to run on regular 97 octane. The Squish height is at 0.6mm. It's pretty extreme. I'm running a Wossner piston kit for some protection over detonation, Still good for a pounding, I except to blow it up.

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    The old Mitaka had created some damage before hand,

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    Mitaka vs Wossner. The quality of these forged pistons is really very good.

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    Shes going to run pretty good. I challenge a 170 kit to outperform this.

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    PowerValve clean up and modified with exhaust port.

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    Both a TZR125RR 4DL 3MB-P-00s, but one is a later Y-2 version with a Non Stamped head, which suggests it came of Belgarda TDR. It's a good baseline.

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    I've done a rough sketch of the port timings between the standard barrel and the reworked one.

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    I had the Top end blasted, and what a difference, worth doing for the money. Now I need an exhaust...



  • @andrew1680 Plug and play bud



  • Have not touched this in months...
    Got it Powder Coated back in January, glad it's done,

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    Cleaned up all the threads, very satisfying.

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    Pro Taper - Henry Reed bend. NOT Kevin Windham's - much to my disgust.

    It's a shame it had to come apart.


  • Global Moderator

    Bit of an odd question, but what tap and die set do you have? My cheapy one is terrible, doesn't have any of the right sizes!



  • @Mightyman I just used 'Dormer' M6 and M8 Metric Coarse (Straight flute) taps. 1mm pitch I believe. Standard stuff, they seem good quality.



  • Great project there, I see you trying a lot of the things I did.
    I had a tm32 carb once upon a time, the only problem was it would overflow because the angle it sits, and if you adjust the floats, it didn't always get enough fuel.

    Also see you're using a YZ airbox to carb boot like I did,.



  • What shock is that mate?



  • @Zrako Its from a 1987' YZ490.

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    Minor Update bits

    Hand sanded and Polished.

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    Ducati 899 Brembo Master Cylinder - 5 minutes to splice the old DTR Brake switch plug on, same coloured wires to.

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    Yamaha TDM900-5PS Brembo Master cylinder - Fits perfect. Frame mounts needs drilling out to M8 is all.
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    Thought I'd post some engine picys.

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    134cc TZR 4DL Topend - Mikuni TM32.

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    1987' YZ125 Airboot - The original DTR Airbox needs only simple modification.

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    @Louis-James Cheers man, I know what you mean about using any other Carb except a TMSS with an angled Venturi. I couldn't run the TM32 to start with.

    I'll use the WR200 Inlet instead, that solves the fitment issues, I use a Reed spacer on the standard inlet and that makes it work well.

    The WR200 Inlet helps to level out the Carb to something pretty good.



  • @Darty that's a good plan, I had thought of a wr200 manifold but that was before I knew you could get new parts for such old bikes haha.
    There are a few pictures of the YZ airbox rubber Installed on my bike on the old forum somewhere



  • @Darty Looking damn good bud!!! 👍



  • The wr200 manifold won't fit unless you cut the back off it as it's too big to fit the dt case's also the holes look to be in slightly different places