Pull Start Reverse pull start?

Discussion in 'Transmission / Drivetrain' started by pickettdeblanco, Feb 8, 2011.

  1. :idea:
    I was wondering if anybody knows of a pull start that pulls the opposite direction of typical cag/gp460 motors? I have spun the cylinder head the opposite direction, in essence, changing the direction of the rotation of the motor in relation to the cylinder with no problems whatsoever. Which leads me to believe there should be no problem running the motor the opposite rotation.

    I ask because id like to lower the weight, amount of parts and cost of my current set up. With a motor driving the opposite direction the need for a jackshaft would be eliminated and a standard pocket bike transmission could be used in place of the staton gear box i currently run and a rear rack mount would be much more compact.

    i suppose the only real issue would be when the coil triggers the spark. After adjusting the timing i dont think there would be an issue. Unless it fires top dead center...?
     
    Last edited: Feb 8, 2011

  2. spad4me

    spad4me Member

    On a gp 460 engine all you did was swap the placement of the exhaust port , and the intake port .
    The engine still rotates in the same direction.
    Most people who do this cylinder flip need the clearance .
    For example hot exhaust pipe too near living leg.
    At one time I tried to find an engine that spun backwards.
    I had no luck.
     
    Last edited: Feb 8, 2011
  3. which is exactly why i did it! As for the rotation i just meant it rotates the opposite way in relation to the original position of the cylinder head, but as i now know you could turn the thing perpendicular if there was clearance.

    i guess the only way to find out is to take off the pull start and try to crank it up the opposite way...?

    if it works i guess i have a new reason to tinker.

    thanks!
     
  4. After some digging it seems the general consensus is that 2 stroke motors would nearly run inside out if you could get em that way... from old 2 stroke boats that would run in reverse after killing the engine and starting it in reverse (which the motor retarded the timing) would run in reverse, to improperly rebuilt motorcycles, to golf carts that had the same feature as the boat. it seems timing in the only determining factor as to which way the motor will rotate, that and which direction you crank the motor up. when i get the time and the funds some research and development is in order.

    I will report back as soon as i have my results!
     
  5. spad4me

    spad4me Member

    The stock gp460 pullstart is trash .
    It will break taking out your flywheel.
    Just a thought remove the funny shaped thing screwed to the fly wheel and make a small slotted drum that bolts to the flywheel.
    Thread a rope through the slot winding in the desired direction.
    Then you could easily try the engine in any direction.
    I am installing a new liner on my 460 tomorrow. So i can understand why you believe that it will run backwards.
     
  6. professor

    professor Active Member

    The only other issue is the ign timing. You do need to change it.
     
  7. motorpsycho

    motorpsycho Active Member

    if you spun the cylinder head and not the jug, it will not affect rotation at all.
    if you spun the jug around putting the intake in the front and the exhaust out the back, the motor will still spin the same way and the timing would still be right because the intake and exhaust ports would stil lbe in the same location as far as the engine knows.
    Unless the piston is notched for the intake or the exhaust. If that's the case then you would have to spin the piston around so the notches match up with the ports, but the engine will still spin the same way.
    I have no idea whay he would have to change the ignition timing because if you rotate the cylinder 180 degrees, it would still fire at the right time. The engine has no idea which side the intake and exhaust is on as far as i know.
    it's not like you are dealing with a cam, lifters and valves like in a 4 stroke.
     
    Last edited: Feb 8, 2011
  8. Ive spun the cylinder head, thats not the issue. i want to make the motor spin in reverse completely. As the professor says ignition timing will need to be adjusted and a new makeshift pull start that cranks the motor the opposite way will need to be fashioned and i should be good to go.

    It just seems like a "less moving parts" alleviation to jackshafts... just make it spin the other way...
     
  9. motorpsycho

    motorpsycho Active Member

    I'm not following what you are trying to do, or why you would want the engine to run backwards.
    are you wanting to have the drive chain on the right side of the bike without the use of a jackshaft?
    if this is what you are trying to accomplish, why not just mount the engine in the frame backwards?
     
  10. Mostly just to see if i can... If i can, it opens up options for simplicity. Instead of having to use a gear box i could just run a chain off of the 1:1 standard clutch bell housing sprocket like most cag motors have for a right hand drive to accommodate for my nuvinci hub.
     
  11. bluegoose

    bluegoose New Member

    right sided driven gearbox, no jackshaft

    i saw this a few weeks ago, hard to get more info, the site does not like answering questions, but it is what we all want, this box is a real mystery. to put you in the picture first go to www.fareastimports.com then look at the bike for sale. for futher info. click on the yellow car on the right of the page, scroll down and see these bikes, the box drives the bikes gears, from the right side. you first turn the engine back to front, This a special reverse drive box, HOW ? can,t find out where this box comes from, the site admin wont tell me. but it will solve your problem and everyone elses that want a motorised bike with gears, sick bike parts won,t be pleased though. even if their kit is good. juat a matter of getting the gearing right. bye bluegoose
     
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