Turning engine around to simplify shift kit

Discussion in '2-Stroke Engines' started by Etpm, Nov 3, 2012.

  1. Etpm

    Etpm New Member

    Greetings,
    This is my first post. I am looking at shift kits for the two stroke engines and it seems to me like there is a lot of extra stuff spinning around with the consequent drag. Since the engines are piston ported and the crankcase opening appears symmetrical, why couldn't the engine crankcase be turned around with the cylinder, and perhaps piston, turned around, and the mag coil repositioned, to make the engine run backwards? This would eliminate the jackshaft, a couple sprockets, bearings, mounts, a chain, etc. Anybody done this?
    Eric
     

  2. adrian101

    adrian101 Member

    to much hard work, its easier to just install a shift kit lol
     
  3. DJ Raizer

    DJ Raizer New Member

    Nothing about this seems extremely difficult... I'm very interested in hearing more opinions on this, as i am not an HT expert. But I am looking into an SBP shift kit for mine.
     
  4. Ludwig II

    Ludwig II Member

    There's a thing engine designers do which is called desaxe. The cylinder is placed a few thou to one side of being truly central with the crankshaft. This reduces load on the thrust face of the piston when power is developed. If you run the engine backwards, as I think you mean, the wrong face will become loaded and failure more likely.

    Check it out, remember the mantra of the old engineers, measure twice, cut once.
     
  5. Etpm

    Etpm New Member

    This desaxe engine designation was news to me. I did a little research and it is indeed used on some engines. And it makes logical sense. Some engines use true offset crank and cylinder bore centerlines and at least one engine only offsets the piston pin bore. In any case it will be easy for me to measure the engine and piston to see if any offset exists. If there is offset, and it's just the piston, then that's no problem because it just involves turning the piston around. If the crankcase is bored to locate the cylinder offset then that would involve re-machining the crankcase bore and possibly relocating the cylinder bolts, way more work than it's worth. Thanks for pointing out the desaxe layout. I'm surprised that I never heard of it in all my years of working on engines.
    Eric
     
  6. Ludwig II

    Ludwig II Member

    I have one of those tribal elder memories. I can't hunt or plough, but I know lots of stuff that comes in useful sometimes.
     
  7. DJ Raizer

    DJ Raizer New Member

    Give it a shot man! If you can pull this off and make it work, it is the key to an optimal shift kit install. Do you figure that adjusting the mag position will compensate the timing?
     
  8. Etpm

    Etpm New Member

    Changing the magneto position will allow the engine to run in reverse. But I don't know yet how this would be done. Maybe it just involves drilling some new mounting holes or making a plate. I own a machine shop so for me it will be pretty easy. If I do decide to do this I will post info for the regular mechanically competent person to follow.
    Eric
     
  9. Ludwig II

    Ludwig II Member

    The rotor/pickup relationship is all that matters. You can mount the pickup in a different place on the casting, or, more simply perhaps, move the rotor round and lap it on to the shaft, so doing away with the key.
     
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