Starting from stops?

Discussion in 'Motorized Bicycle General Discussion' started by adamg4119, Jan 23, 2011.

  1. adamg4119

    adamg4119 New Member

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    Just a general question here, why cant 50cc motorized bikes start from a stop (a light or a stop sign) but 50cc mopeds can? is there a way to allow this?
     
  2. Elitefr

    Elitefr New Member

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    because these little engines have friction clutches and the more advanced moped engines have centrifugal clutches. google it
     
  3. 2door

    2door Moderator
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    Many factors come into play here. Rider weight, gearing, the power output of a particular engine and how easy the clutch is to control. First you have to consider this basic fact. It isn't a motorcycle. It is a motorized bicycle with a limited horsepower engine and an imperfect clutch design. They are designed to be pedal assisted and that usually means that from a dead stop you need to pedal to take some of the pressure off the clutch pads and engine to overcome inertia.
    A bike with a large rear sprocket, low geared, will be easier to start from a stop than one with a smaller, higher gear sprocket. Many owners who have done no clutch linkage modification will find it difficult to 'slip' the clutch with the handlebar lever, however there are things that can be done to allow slow, easy application of the clutch making a dead stop start possible but it still puts undue wear on the clutch components.
    Even with a centrifugal clutch, helping the bike to get rolling with the pedals is a good way to increase clutch life.
    Horsepower and torque are also considerations. The Mopeds you mentioned might be 50cc but they might also produce more 'umph' than the standard, unmodified China Girl.
    Tom
     
  4. msrfan

    msrfan Active Member

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    Right on, 2door. Also, my Motobecane has a variator clutch which has three centrifugal circuits. One for pedal starting, one for taking off from dead stops, and a pulley system giving it a transmission. Very low gears for starting, transitioning into a higher ratio for speed. On the other hand, My Garelli has an internal wet clutch that is very efficient and does not overheat. That is not to say that the chinese clutches can't be improved. I think I saw someone on this forum experimenting with different puck matrerials. McMaster Carr sells clutch and brake material with different friction ratings. Have to be careful not to go with a real hard lining and warp the plates. A shift kit (jackshaft) solves most of the take-off problems. Even my Whizzers and Briggs bikes with slipper belt clutches won't take off from a dead stop without squealing and grabbing. Automatics solve the problem when you have 4-5 hp, otherwise give the pedals a few strokes and let the clutch out on a roll.
     
  5. adamg4119

    adamg4119 New Member

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    thanks guys for the heads up
     
  6. scotto-

    scotto- Custom 4-Stroke Bike Builder

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    I have a 49cc 4-stroke on my bike and it starts off the line with a brnot followed by a .wee. and just goes like a "bat outta hill" after that!!! :D

    Seriously......laff
     
  7. wayne z

    wayne z New Member

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    What kinda tranny u got please?
     
    #7 wayne z, Jan 23, 2011
    Last edited: Jan 23, 2011
  8. wayne z

    wayne z New Member

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    I have no trouble taking off from a dead stop on my cruiser with 66cc slanthead with 41 t sprocket without pedaling at all.

    These engines have a LOT of low end torque for their size. With a little finesse, it's easy to feather the clutch along with low throttle and engage the clutch early at low RPM , then smoothly accelerate.

    So what if the clutch pads need replacing early, they cost about as much as a McDonalds meal :~)

    DSC_1398.JPG
    I never pedal, unless a cop is watchin' too hard
     
    #8 wayne z, Jan 23, 2011
    Last edited: Jan 23, 2011
  9. Allen_Wrench

    Allen_Wrench Resident Mad Scientist

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    Another factor to consider: 50cc motor scooters have much smaller wheels too. Look how big our 26 inchers are. That's a lot of leverage that the little HT China gurl needs to put out. You're workin' her like a slave when you try to get her to start off the line. Those little scooter wheels don't need all that, and with a centrifugal clutch (and some even have a two-speed tranny) there's no pressure.
     
  10. mybike

    mybike New Member

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    My chopper has 48cc starfire 2 cycle chrome with a centrifugal clutch. I start off with dead stop NO problem . 50th rear sprocket.

    Mybike
     
  11. Goat Herder

    Goat Herder Gutter Rider

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    C clutches are a little different than the manual clutches. I gotta recon they will take way more abuse. Yet still wear and tear wise why not just a bit of peddle of the line with it? That is still better on the motor..
     
  12. bitsnpieces

    bitsnpieces New Member

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    Definitely; I'm getting better at pedal starting and it sounds like it works wonders.

    Without it or proper pedal start, I can hear the gears kick in and just sounds mean.

    Imagine trying to pull something and you suddenly just tug and pull compared to getting a good grip and slowly pulling harder and harder, both works, but there's a difference in how your arms will feel at the end of it.
     
  13. Black_Moons

    Black_Moons New Member

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    I use the clutch to take off all the time.. its probley not good for clutch life however.. I do it via the following method:
    Rev the engine to medium/high revs, SLOWLY release the clutch untill rpms start to drop, Then you open the throttle wide open as you slowly release the clutch a little more over a few seconds.

    Takes a little pratice not to overrev or stall out.
     

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