Reed valves

  • Global Moderator

    I didn't check my reeds when rebuilding the engine but just wondering what sort of impact warped/bent reeds would have on the running of a DT/TDR engine? Very noticeable? I will be checking them soon and will replace with carbon fibre reeds if they do need replacing.

  • Mine were good but I did upgrade to the carbon ones from eBay chaos stage 1 I believe, instantly as soon as I started it you could feel the throttle more responsive admittedly it didn't make loads of difference but the bike did seem to rev more freely I think it's all the little things that add together to make a complete package reeds should be a must, I've already ordered another set for my next project.

  • Administrator

    See they would make difference back in day. But the reeds that come as stanadard are made of a decent plastic that gives the same properties as the carbon ones. I personally didn't notice any chanhe, but for the money would buy again purely for bragging rights.
    Bent ones should be down on power and fuel. You might find it starts to hesitate and use more fuel

  • Funny you say that calum mine is drinking fuel lately I always use super unleaded from tesco but i seem to always be filling up

  • Global Moderator

    @Calum @andrewj1680 definitely worth giving them a check then by the sounds of it! 👍

  • Administrator

    So just to clarify:

    Reed Valve /Torque Induction

    The reed valve, formerly known as Torque Induction was a system developed by Yamaha to solve the problem of spitting unburnt fuel back into the carburetor.

    Previously the carburetor sat as the inlet, air/fuel was sucked through the vacuum created by the piston upon induction. However during compression the fuel was able to flow back into the carburetor.

    Kawasaki answered this problem with the rotary discs, but it wasn't until Yamaha developed the reed valve did the problem of keeping it simple was solved.

    Effectively, as the name suggests, the reed valve operators in a similar fashion as to how they would on a wood instrument, effectively air can pass through the reeds as the force exerted on them causes the reed to lift, however the back pressure won't cause the reed to open.

    You effectively create a really simple one way system.

    If the reeds are bent then fuel and air can come and go on compression and induction. So fuel is going to be spat back into the carburetor. Power is going to be down as fuel atomisation is effected due to the turbulence created.

    As the power of an engine increases, so must the rigity of the reeds. At high power/rpms you can cause an effect known as Reed Flutter. What happens here is that the force exerted on the reeds as induction occurs causes the reeds to bounce on the cage, when the RPM's are high, the bounce could carry over to the compression phase, cause fuel/air to be forced back into the inlet track.

    Stiffer carbon reeds are less prone to reed flutter, hence why they are considered an upgrade. However YZ125's come with the same plastic reeds as the DT as standard. If it's good enough for 33bhp+ it's good enough for 15. But an upgrade is an upgrade never the less. It is probably cheaper to get carbon ones than OEM plastic ones.

    Hopefully that clears any misinformation up.

  • @Darty @Calum would the boyseen reeds be any better than the carbon ones off eBay? I was going to ask this question but found this thread. They claim to have an effect on performance but the carbon reeds on eBay don't 🤔 I personally imagine they are the same anyone know?

  • Administrator

    I run these

    Everybody loves a bit of CF.

    I don't get the point in the Boyseen if they are just plastic, how are they better than OEM. At least the carbon ones are carbon

  • @Calum

    I quote...

    : Please Note: Only CF part numbers are carbon fibre (HT part numbers are not carbon fibre) ?? These are not even Dry carbon?

    I have to add, that Carbon reeds are very stiff, it's actually less than ideal for the DT.

    Stick to plastic I say, Boyesen follow production specs, which are ideal to start with.

  • Administrator

    Looked like carbon to me


  • They look sick, trouble with Carbon fibre is it does not flex fluidly and fractures like a bitch..

    I am dubious of having one rip itself apart into the crankcase,

    I've got a CR125 MotoTassinari VFORCE 3 Reed block to try on the DT,

    Will post results, should clean up the Mid-range RPMs a little bit.

  • This dude on ebay sells carbon reeds for all DT's;

    He also does a stage 2 kit as well, but doesn't have any listed ATM sadly!!! 😞

  • No very noticeable, although my v-force v3 works very well, especially in the high revs 🙂 see my 200cc conversion thread


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