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Derestricting

Return the bike to how it was intended to be!
23 Topics 376 Posts
  • DERESTRICTING GUIDE

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    @NINJA
    Sound 👍

  • Yamaha Dt125RE/X Stock Exhaust Pipe

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  • Yamaha dtr

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    N

    I wanted to make it work with the power of the cdi magneto, but my servo burned through. I dont know what i did wrong and i want to figure out before i put the new one on

  • Restrictions

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    Hark_PtooieH

    Quick answer since I have a 2002 as well (DE03):
    1 - Swap expansion chamber (the blobby exhaust bit) to an Athena or something. This was the big thing.
    2 - Pull out the reed switch from behind the speedometer. Do not disconnect it or cut any wires, just wrap it in tape and stuff it aside. It detects when the needle gets to ca 80 km/h and cuts ignition there.

    That should be it, your bike should now rev freely to 9500 rpm and do 120+ km/h.

    Also: ensure that the YPVS is working as it should. Remove the round cap on the left side and turn on ignition. It should rotate back and forth a little, then settle such that the groove on top is right over the hole.

    Explanation on that last bit: The YPVS switches the port timing between low revs (more torque) and high revs (more power) as the revs increase and decrease. Variable valve timing, you could say.

    When you turn on the ignition it rotates back and forth (flips between low and high mode) to scrape off soot. The resting position should be over the hole because they used that hole to fixate the valve in low-revs mode (and turning off or removing the solenoid actuating it) when they restricted bikes, but I believe they stopped using that method after 1998 or something. If it does not rotate back and forth with an audible "bzzt-bzzt" when ignition turns on, your YPVS is not working and stuck in either of the modes.

    As for the inlet manifold I did a thorough CFD analysis and found that you cannot improve it. Leave the plastic bottle on, it smoothens out the gas flow. The carburetor should not need anything either, it is likely a Mikuni TM28SS with a 240 µm main jet, which is perfect.

  • Derestricting kits

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  • Derestrict yamaha dt 125 r 1997

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    Mr ShadiM

    @markus-w
    You told me to cut the wires and keep them apart lad. That didn't work, what i did was i cut the wires and connect them at the right time to somehow bypass the restriction.

  • Missing reed switch

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    @Hark_Ptooie

    It’s a bit of a headfux isn’t it? The read switch might not be a simple magnetic on/off by the looks of it. It might set to a default mode if it the CDI doesn’t detect a continuity in the curcuit?

    @Blasterguy
    It would be helpful to know if it only restricts the revs in top gear, or every gear? I would try joining the wires at least once to see if there’s a change at all…

    It might be easier to get an earlier CDI than a read switch…

  • Need to verify my bike year and model so i can look for restrictions

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    @SpookDog I'll inspect the power valve from the exhaust port and try to post pictures later, just to be sure
    The bike feels fast and has good acceleration so there's a possibility that it's just my speedometer that's screwed up LoL

  • Servo motor issues

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    Hark_PtooieH

    1997:
    Screenshot from 2023-09-04 00-57-29.jpg

    Hilarious thing, but it developed a plenitude of electrical problems that I was to inept to manage, so I sold it cheap. Regrets.

  • About the rubber intake manifold.

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    CalumC

    @SpookDog Me on my 170 🤣 No maybe not quite that low, but that's what I've come to appreciate with the Yamaha now.

    You look back 15 years ago when I first used the Athena kit and you'll see a completely different opinion from me.

    But now I have my other screaming two strokes, I am happy to have a DT which doesn't need to be revved to the moon to enjoy. But oh boy I've had some good rips home from work this year on the DT 🙂

  • Yamaha DT 125 DERESTRICTING

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    I'm sorry for my inactivity... Thanks, everyone for helping me out! I opened the power valve and removed the rubber tube that is on top of the airbox. Now the bike gets much more air and breathes as it should, it goes like a beast. THANKS, EVERYONE!!

  • YAMAHA DT 125 E SWISS

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    Yeah, go through the derestriction guide.

    Only when you know it’s properly deristricted can you address why you’re only getting 55-60 mph from your bike. Cause that’s not right restricted or not...

  • 1992 4bl electric start model. Advice please😁

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    dt200wrmanD

    @Calum ok mate. Il speak to him about it

  • 1989 French DTr REV LIMITER?

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    NINJAN

    @Coreyp90 There's a full derestricting guide pinned to the top of this section. It covers all years and is most informative. 😉

  • Lighten a fly wheel

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    CalumC

    @declan You can take them off.

    Inner rotor kits. But they are not practical for the road. Kill engines and no good uphill.

    But for a flat track they're fine.

  • Can anyone offer any advice

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    @NINJA thanks

  • 2003 DTR Powervalve issues

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    @calum ok cheers

  • This topic is deleted!

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  • Derestricting 97 DT125r

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    @calum said in Derestricting 97 DT125r:

    @sloanparkes Sounds like the powervalve isn't set up to me.

    Ya well I've moved it back the other way... but it doesn't reg above 65000 in 5th and still sat at 60mph ish I'm so sure it's restricted...

    And ya @NINJA it was right at the bottom and my toolbar on my phone was covering it saying 97 to 99 😧 cheers dude

  • Yamaha dtr 1999 125cc

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    @giorgio95 Must be first DTR with cdi on the back of the oiltank ? Wire in speedo you messed with white/black from the reed switch ? Thats linked to the cdi then ypvs servo. Sounds like it could just be a bad connection in the circuit somewhere if its kicking in when you move it.

    Easiest and proper way to set the ypvs cables on the pully wheel under the cover is like this.

    On the pully wheel in between the cables is a notch in the wheel, when you switch your ignition on and the ypvs spins over its cycle when it comes to a rest the notch should line up with the dot directly behind it. If it does thats it set properly just make sure the cables are tensioned up ok. Same applies if you have to adjust them to get it to line up and then your good to go.