Backward engine.

Discussion in 'Motorized Bicycle General Discussion' started by ferball, Mar 25, 2011.

  1. ferball

    ferball New Member

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    I know there is an entire thread about an engine with jug reversed and a few other things, but I did not find simple yes or know to this question. If I install an engine backwards will it run in reverse with out a an issue? It is s single cylinder two stroke, so I would think in theory if was started running in reverse it continue with out a problem but I was just wondering if theory and reality agreed on this point.
     
  2. adb140275

    adb140275 New Member

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    golf kart engines run backwards for reverse... theres no reason they wont run backwards unless they're rotary induction, which these engines are not. if you for whatever reason install the engine backwards, you cant drive the rear wheel.
     
  3. skjjoe

    skjjoe Member

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    Are you talking about turning the cylinder 180 degrees so the carb is on the front . is this a china ht engine your talking about. I need more details and I might be able to help as I have "flipped the jug" on mine.
     
  4. ferball

    ferball New Member

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    I had an idea for an interesting install, that engine would be installed backwards putting the drive sprocket on the right side of the bike, but instead of running it to the rear sprocket run the chain forward. But as I thought about more and more it made less and less sense.
     
  5. ferball

    ferball New Member

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    I am curious about the flipped jug as well. Is it as simple as taking the jug off and rotating it? because that would help solve some of my build problems, but I know enough about engines to know that I do not want to modify the internals, even on a cheap HT.
     
  6. skjjoe

    skjjoe Member

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    the engine does not run in reverse with the jug flipped it runs the same direction as it did before flipping the jug. I couldn't tell you how to make it run backwards.
     
  7. adb140275

    adb140275 New Member

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    if you flip the jug youll have to modify the transfer ports or it wont run for crap, unless they are symmetrical....... which they arent
     
  8. skjjoe

    skjjoe Member

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    you do have to mod the internals to do this some of the issues are
    Rotate the piston so the rings dont hang up on a port
    Matching the transfer ports in the case and cylinder
     
  9. skjjoe

    skjjoe Member

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    Not some thing I would recommend. Unless you are very confident in your mech ability and understanding of the ports inside the engine
     
  10. adb140275

    adb140275 New Member

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    leave the jug on the way it is and just have fun porting it. i still need to make a port map of one of these things to tell you what to do
     
  11. scotto-

    scotto- Custom 4-Stroke Bike Builder

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    I'd just go to Google earth....they have maps of every port imaginable.....laff















    sorry, I couldn't help myself rotfl
     
  12. Nougat

    Nougat New Member

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    Two stroke engines will run just the same turning in either direction. There's a handful of old cars that were built with two-strokes; if you get it rolling forward, and then bump start with the transmission in reverse, normal reverse becomes a single forward gear, and the others become multiple speeds in reverse.

    It's not out of the question to completely reverse mount an HT motor, but it would require some creative work at the mounting points.
     
  13. skjjoe

    skjjoe Member

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    I port matched the transfer ports on mine using silly putty . man that stuff is good for allot of things like that. I also used it in the case to keep metal shavings from going places I didnt want them. The shavings stick to the putty and you just pull the blob out shavings and all.... A good rinse and your good to go.
     
  14. Allen_Wrench

    Allen_Wrench Resident Mad Scientist

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    Here's why I'm confused: when you say "run the chain forward" are you talking about driving the front wheel? If so, won't steering become a problem? The other issue is this: when the engine's drive sprocket is on the left, it and the rear wheel turn counter-clockwise. If you mount the engine backwards with the drive sprocket on the right, no matter which wheel you power - it will still turn counter-clockwise, meaning that on the right side of the bike you would indeed go backwards, i.e. in reverse. Unless you rebuilt and modified the engine to compensate.

    Might I suggest a jackshaft to accomplish something similar.
     
  15. dmb

    dmb Active Member

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    every good port has a liquior store right? no... port is left.
     
  16. ferball

    ferball New Member

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    Like I was saying the more I thought about it the dumber it sounded. But my thought was this: I am making a long wheel base recumbent, I was thinking of turning the engine around and running the chain forward that hooked to a jack shaft that would be integrated with the front cranks then back to the drive sprocket so that the cranks and the engine hit the drive sprocket on the same drive chain so I could shift, as you can tell from my description is convoluted and overly complicated and like I said it got dumber and dumber the more I thought about it.
     
  17. bairdco

    bairdco a guy who makes cool bikes

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    i thought someone here made one of these engines run in reverse, but the timing was completely off so it didn't work too well.

    i know that most two strokes can run backwards, so once i "fakied" my bike backwards down the driveway and bump-started it. luckily, it started normal (forward,) otherwise i woulda been over the bars with my bike in the street behind me.:)
     
  18. wayne z

    wayne z New Member

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    The HT could be made to run backwards by cutting a new keyway in the magnet rotor or crankshaft, to get it to fire at about 25 deg btdc of new rotation direction.

    You might hafta take extra measures to keep flywheel and sprocket nuts from backing off.

    I useta start my allstate moped by backing it down an incline in first gear. It would run but poorly.

    When I roll my Hongdu/Solex backwards with the comp release on, It pops a little
     

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