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  • Top End Related
    55 Topics
    668 Posts
    S

    My 3nc is fine as well. But nobody said they were bad. Just that the 3mb were a tadpole better 😜 …
    With the early bikes a fat strong spark can make a real difference. As soon as I put my lights on it zaps my tick over. I can see it going from blue to orange in my minds eye! …

  • Bottom End Related
    7 Topics
    42 Posts
    Hark_PtooieH

    Sorry for commenting on a 3 year old thread, but I have worked a little with balance shafts on humongous machinery and wanted to post a little for posterior knowledge.

    A single balance shaft on a single-cylinder doesn't really do much. It mostly just phase-shifts the vibrations so they go in another direction. Back and forth instead of up and down, like.

    Dual balance shafts is another thing. They cooperate in the right direction, and counteract each other in between - and if you put them slightly offset each other vertically they can even mitigate some rotational moment.

    But balance shafts also have another interesting effect - they can reduce the bearing load. There are actually two different optimums - one which gives the least vibrations but a bit higher bearing load, and another that is the opposite.

    So when I see that small engines have a single balance shaft, I usually assume it is to allow it to manage high revs by means of lowering bearing forces rather than reducing unpleasant vibrations.

    There was a bike back in the 90's(?) - some european single-cylinder 2-stroke 250 cc enduro (cross?) - that had a balance shaft and managed to output 70+ hp when all the balance-shaft-less big-brand competitors only gave 55 hp or so. Because it revved to like 12000 when the others quit at 9000 or whatever.

  • Carburetor Related
    93 Topics
    954 Posts
    Hark_PtooieH

    The cylinder sucks in air at intervals, leading to a pulsation in the inlet airflow. That bottle is a buffer that smooths out the pulsations.

    The piston goes up, sucking in air through the carburetor which is (and should be) the main restriction in the intake. This causes a low pressure on the engine side of the carburetor, including that bottle.

    When the piston goes down and closes the intake port, there would be a rather sudden pulse where air rush in through the carburetor and meets a dead end. Pressure rises, gas stops throughout the manifold, including the carburetor. Then when the port opens and the piston sucks in gas again, it would have to accelerate the gas mass from zero.

    With the bottle, the volume of that closed-off manifold is artificially increased, so it takes longer for the gas to fill the cavity and come to a stop. Hence it keeps moving, supposedly until the port opens again and the piston suck in gas again.

    The effect should be that there is a more constant flow of air through the carburetor, which likely improves the atomization or decrease condensation or whatever.

    4-stroke engines usually tune the intake manifold runner lengths such that the air pulsations should cause the "pillar of gas" that comes at the intake valve at high speed should "ram" through it when it opens. While the mass of the air is small and it is very elastic, the velocities are substantial so it counts. I wager this is sort of the same thing.

    In 4-stroke engines it is also not uncommon that the intake runner lengths vary with engine speed. I know my car has a valve that opens and shorten the length above some rpms. My Honda Fireblade also had something like it in the airbox.

  • Return the bike to how it was intended to be!
    22 Topics
    368 Posts
    C

    @Calum said in Restrictions:

    @tunertom Yeah that inlet manifold is a load of tosh, but don't discount Scrim, he knows his shit.

    @CYBER-NINJA haha yeah I did chop my exhaust up and removed the cat, but oh my seriously those pipes have some serious weight, so if not for the performance the weight alone is worth swapping out lmao!

    Hi I have his destruction manual and seems mostly since 🙂

  • Choppy power band

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    CalumC

    Happy days 😃

  • Resonator build thread

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    1 Votes
    4 Posts
    121 Views
    R

    @Rallyfinnen I think you might be right about the timing angle, one of my repeated measurements came out as cca 185°. I could have used the wrong technique when measuring; Shined a flashlight through spark plug hole and basically measured between the times I can see any light coming through, used the magnet rotor to set marks. A solid, definite number would be useful; my machine has a 3MB00 cylinder and a standard thin gasket, it is not marked with "P" and has never been bored or ported.

    As for the temperature, I didn't get reliable numbers with a multimeter probe at the flange with the exhaust off, so I opted for calculating it via BMEP which turned out right around 7.10
    The temperature would be lower at the middle of the pipe and even lower at the convergent cone, the highest temp is supposed to be right at the exit of the cylinder and if I'm not wrong, that's the part that creates the pressure wave.

  • Fly wheel weights

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    M

    @Calum that’s makes sense you seem pretty knowledgeable on the bike front pal

  • Airbox mod

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    3 Posts
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    M

    @Calum to be fair I did read it for the 200 engine, but I also remember my 125x having let’s say a 40mm hole cut in the side of the air box with some mesh that was done when I purchased it, so now idea if it benefited from it or not

  • V force reeds dt

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    declanD

    @dan28 yeah I did it as I said the blaster 200 are a better fit the cr 125 ones are a little too small but you can make them work

  • Unburnt oil from ypvs Left side help

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    S

    @waale2004

    You changed the seal as well as the o~rings. I don’t know if the Athena kit uses special or standard parts? 2 o~rings & 1 bush seal. These are the only parts that can be a problem...

    Do you premix 50:1?...

  • inlet 38mm

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    CalumC

    For completeness

    alt text

    This is my old inlet manifold that I opened up to easily accept larger carbs.

  • DTR Ignition Maps & Timing

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    M

    @Calum Ah ok. Thanks

  • DT 230 Lanza engine parts from china

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    declanD

    @Sven-Hackbarth there was already a thread on this it’s a good looking bike and more parts is never a bad thing in my experience AliExpress is pretty good quality I like the carbs especially

  • How to adjust the power Valve

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    322 Views
    DTleeD

    Thanks mate

  • Carb setups.

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    783 Views
    Walney-ReptilesW

    @frazer-c i know this is an old post but i know a site were you can get flat carbs from for the DTR not sure if im allowed to post the link tho.

  • Cylinder head tuning and machining

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    Glynn123G

    @Calum I'll take a picture of the head I've got, it's stamped 3MB but it's the one with the ridged, I'll have a look at the book cheers
    I planned on skimming the deck down at the end to create slightly higher compression than standard ideally

  • 3 Votes
    6 Posts
    769 Views
    P

    I didn't need to read that, damn it :grinning_face_with_smiling_eyes:

    Good read.

  • 3MB00 "P" barrel, head and powervalve

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    779 Views
    T

    Hi, what is it you want to buy. cheers🙂

  • Power valve rotating one way then stopping

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    311 Views
    NINJAN

    @shally Which company is doing the test & repair? Share a link if you have one please???

  • 1st gear plug chops?

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    declanD

    @Glynn123 yeah but I’ve heard loads over the years about what you have to do to push the bikes without getting it impounded but the problem is practices change from one police branch to another and my specific police impound no matter what they essentially do what they want all of the main criminals and such have the police payed off so there’s no way I’d chance a near 2 grand bike)

  • DTR 200cc ignition map

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    R

    No worries. I will start with the RE curve and go from there ☂

  • Derestricting a 2002 DT125R

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    NINJAN

    @Bluestoesonnose See hear for the 411 bud;

    https://dt125r.co.uk/topic/578/derestricting-guide

  • Jetting help

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    R

    Okay I'll Do a plug chop when I get chance they normally come out black because I premix and all ways
    Tend to do the mix a little rich to be safe I deffo think it needs up jetting tho

  • Best powervalve setting for higher revs?

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    19 Posts
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    declanD

    @finnerz89 😓