Clutch Why a Transmission ?

Discussion in 'Transmission / Drivetrain' started by Manic Mechanic, Sep 15, 2016.

  1. Manic Mechanic

    Manic Mechanic New Member

    What is the purpose of a transmission on a 4 stroke Predator engine. Why can't I just put a clutch on the 3/4 shaft and leave it at that.

  2. Simple is a great thing!
    As long as everything lines up, and you get the desired ratio you want, simple is great!
  3. skyash

    skyash Active Member

    I've seen go kart clutch on the shaft never seen a transmission
  4. Manic Mechanic

    Manic Mechanic New Member

    thanks for getting back to me.
  5. MotorBicycleRacing

    MotorBicycleRacing Well-Known Member

    The fact that nobody does that might be a hint that there are very good reasons.

    Everyone buys or makes a jackshaft aka "transmission"

    You nailed the 2 reasons why a jackshaft or CVT is used.
    Last edited: Sep 17, 2016
  6. MotorBicycleRacing

    MotorBicycleRacing Well-Known Member

    Now I see that you didn't mention in your question, "Looking into building a 4 stroke rear drive bike that has the proper brakes for safe stops"
    A 212 cc mounted on the rack overhanging to the right so the chain lines up is one heavy cumbersome beast......
    How much does a 212cc plus clutch weigh?

    Be aware that cheap centrifugal clutches jerk and grab with a 212 cc.

    I see you are in Socal so I am inviting you out to the Sat Oct 22nd race at Grange Motor Circuit in Apple Valley
    Come on out to see the state of the art in motorized bicycles.
  7. Manic Mechanic

    Manic Mechanic New Member

    I would probably use the 3hp predator if I remember correctly it weighs 22lbs.
    Who makes the best centrifugal clutches ? Apple valley sounds great. I will try and make it.
    Thanks for your input, Manic Mechanic
  8. Manic Mechanic

    Manic Mechanic New Member

    Stopping was a major issue on my last bike. I was going to use a single front disc and rear hub on my next one. Still not sure if this is enough. Manic Mechanic
  9. MotorBicycleRacing

    MotorBicycleRacing Well-Known Member

    You said 3/4" shaft so that is a 212cc. 79 cc has a 5/8" shaft. :)
    Gearing ratio from the clutch to rear sprocket will require about a 100? tooth sprocket.

    Why don't you put the 79cc motor centered in the frame? you will need a jackshaft plate, wider pedals, etc.

    Look up Shane at in Santa Barbara for clutches for a 79 cc.
  10. JunkyardDog

    JunkyardDog Active Member

    You need a transmission because the powerband on an engine is fairly narrow. A transmission will allow you to keep the engine in it's powerband at different road speeds. My 225cc motorcycle will not go over 15 mph in first gear at full throttle, but it will go 70 mph + at full throttle in 5th gear.
  11. Manic Mechanic

    Manic Mechanic New Member

    I stand corrected, 5/8 shaft, thanks. I am not committed to any one engine at this time accept I want it to be a four stroke. I found the 2 strokes not as reliable as I would like. I know everyone is telling me I must have a transmission but I would like to eliminate it. Having one must rob a lot of hp. I probably will have to install one, but as for right now I am in the research mode. I am also interested in a couple of bikes but both companies have shitty reviews. Happy riding, Manic Mechanic.
  12. CrazyDan

    CrazyDan Active Member

    Very few of us mbers run real transmissions, what you are thinking of is known as a transfer case. It drops rpm and increases torque, but is stuck at one ratio. A true transmission has multiple ratios.
  13. CrazyDan

    CrazyDan Active Member

    I live around the corner in Yucaipa but there's no way in hell I'm gonna try going up the Cajon Pass on my bike...otherwise I'd attend :(.