Centrifugal Centrifugal clutch and Start from zero (with no paddling)

Discussion in 'Transmission / Drivetrain' started by Ronen, Dec 20, 2015.

  1. Ronen

    Ronen New Member

    Hello, I have a 80cc chinese with regular clutch,
    I want to buy a centrifugal clutch in order to start from zero without paddling
    and I have some questions:

    With Centrifugal clutch, when the engine is already running,
    is it possible to just pull up the throttle from zero Mph and start rolling without touching the paddles at all?

    And what is jackshafting and friction drive?

    Thanks, Ronen

  2. crassius

    crassius Well-Known Member

    I've seen many heavy weight riders do that - not sure if it wears the clutch tho.
    Ronen likes this.
  3. KCvale

    KCvale Motorized Bicycle Vendor

    To use a cent clutch you also need a pull start.
    There are kits to convert these engines that way, but they require some expensive mods and not reliable.

    All* 4-stroke engines have a pull start and cent clutch, and no, you never have pedal the things.
    Give it gas and goes.

    A shift kit (jackshaft) transfers the drive power to the right hand side so you have no left side chain and the engine power can use your bicycle gears.

    Like this.


    Pull start 49cc with auto clutch and a seven speed drive.
    It will pull a wheelie from the the line in 1st and haul ass up to 40+ using the gears, and never pedal but you can if want.
  4. Fabian

    Fabian Well-Known Member

    You do not need a pull-start with the centrifugal clutch on the 2-stroke Chinese bicycle engine, but the pull-start is a handy item to have installed.
  5. KCvale

    KCvale Motorized Bicycle Vendor

    A centrifugal clutch is a one-way power transfer system.

    When the power side of the clutch, where the engagement springs and shoes are mounted on the engine, they move out when they spin fast enough to engage the inside of a fixed size bell that connects to the rest of the drive system.

    When the engine is not spinning fast enough to overpower the springs that hold the engagement shoes against the bell, they don't make contact or transfer power.

    Your wheel side is connected to the bell side of the clutch.
    It's just a piece of cupped metal that grabs the retracted clutch pads when they spin out fast enough to make contact, and passes the power on.

    If the engine is off, the shoes are retraced and don't make contact with the bell.
    You scan spin that bell all you want, it's not going to shrink in and grab the shoes.

    You CAN NOT make a Cent. clutch transfer power from the output side, which includes trying to bump start a 2-stroke engine.

    They are great benefit to an automatic clutch, I love them, but you need another way to start the engine regardless.
    Last edited: Dec 26, 2015
  6. Fabian

    Fabian Well-Known Member

    You are giving bad advise, as the commonly available centrifugal clutch CAN be used in pedal start mode on the 2-stroke Chinese motorised bicycle engine.

  7. johnsteve

    johnsteve Member

    interesting video, but where do you get the parts? Could you please put a link to the place where they can be boughtt?

    also since I am a beginner at these type of things, I have to ask if wd40 is really good lubercation for the crankshaft extension bearing? I would imagine that the possibliity of burning up the bearing probable. would it now be possible to use a heavier lubercant?
  8. Fabian

    Fabian Well-Known Member

    I have never said that you should be using WD40. Please read the description in the video.
    You can simply Google pull-start pedal-start centrifugal clutch to find out where this item can be purchased, but i bought my centrifugal clutch through JN Motors.
  9. skyash

    skyash Active Member

    All my bikes take off with no peddling a 66cc 26 Inc wheel 44 or 36 sprocket a 49 cc 4 stroke with a 20 Inc wheel 52 tooth sprocket and a 49 cc 2 stroke pocket bike motor 20 Inc wheel and 52 tooth or 44 sprocket. I like that you can start when pedalling on a 66cc a pull start is bad that it sucks to pull it on the go and it can brake my 49 cc 4 stroke just broke it's gearbox and it's new The chain inside come off I don't know y and is loose as now
  10. Ronen

    Ronen New Member

    With this clutch without a pull start installed, is it better to just pedal till it starts or pull the regular clutch and pedal and then release it?
  11. Ronen

    Ronen New Member

    I just ordered from JN motors, it was out of stock and then there was one so i rushed to buy it but I'm shure thei'll bring more so just contact them here's link: http://www.jnmotorsbikes.com/product_p/jnm1166.htm
    heres from other stores: http://www.gasbike.net/Centrifugal-Clutch-Kit.htm
  12. KCvale

    KCvale Motorized Bicycle Vendor

    (sigh) That is far from common, the clutch bell is not only on a freewheel, it is directly connected to the engine and has the spiral gear to connect to the output to spin the bell when you pedal.

    That IS NOT spinning the clutch bell and expecting it to engage the clutch pads, which is all I have ever stipulated and simple fact.

    Since that design has taken away your manual clutch, whenever you pedal it pulls the motor.

    Note he doesn't show starting it?
    Ever try to bump start a 2-stroke from a dead stop without drag-free pedaling to get some momentum to help?
    Even worse, you have to drag the whole engine when you want to pedal the bike with engine off!
    Best hope you never run out of gas or just want to push the thing around, if the wheel moves forward the engine turns with compreesion and tries to start.

    All that special fabrication of special parts and all it does is let you not pull in the clutch to stop with the engine running?
    That has to be worst trade-off in the history of 2-stroke MBs and the only bad advice in this topic.

    Hi JohnSteve, this is just a dumb thiing to do for anyone, especially a NooB.
    WD40 is a solvent not a lubricant, the video reference to it was a poor example for the cans lift up straw spray can, I don't know of any actual oil like that so why he used it as a reference is beyond me, but then again so was the whole contrived object of it to begin with.

  13. Fabian

    Fabian Well-Known Member

    Starting the engine is no problem at all, if the carburettor is jetted optimally, but that goes for any engine.

    I have never advised to use WD40. I have simply used the reference for the applicator tube or nozzle, as most people know what WD40 is, and the applicator nozzle happens to be 2.35mm external diameter, of which the hole in the gaskets and bevel gear are 2.5mm in diameter.

    I have made specific note in the video description of the the best aerosol lubricant to use.

    The manual clutch is retained, allowing you to pedal the bike without the engine operating.

    And lastly, the centrifugal clutch is surprisingly reliable, when making basic reliability upgrades. The centrifugal clutch is also the best thing since sliced bread, for once you have used it, you will never go back, especially if doing heavy haul or serious hill climbing; having to inch the bike forwards over difficult obstacles, but in general, the centrifugal clutch is a "must have" option.
  14. KCvale

    KCvale Motorized Bicycle Vendor

    Maybe I missed that in the video, all I saw was tightening the flower nut tight to make the pads one with the pressure plate.
    I agree with Cent clutches, with a pull start, like an automatic over a stick shift in a car, darn easy to ride.