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About oldwing

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  1. oldwing

    st90 engine in a ct70

    In regards to the original question I've learned that the ST90 engine is nowhere near a bolt in for the CT70 frame. The ST actually uses 3 mounting points to hang the engine and sits further back in the frame. You would have to remove a considerable amount of material from the CT frame and modify the lower mount position rearward, add a mount where the isn't one between the upper and lower, and reposition the brake lever mount as this is where the lower engine mount would now be. The upper mount location stays in the original position. It's just not worth it. 88cc kit will do nicely thanks
  2. oldwing

    st90 engine in a ct70

    Well as it turns out I've aquired a complete ct70H bottom end, complete with 4 speed gearsets and manual clutch. Lucky, Lucky!! Next question-- can you use a z50 head on a ct70 cylinder? I've got a z50 head that just needs valve seals and a gear cover, and I've got a standard bore 72cc piston, just short the cylinder. Is the z50 combustion chamber any smaller? Valves smaller? piston cutaways for valves different? I'm really hoping the K2 Z50 head will work, let me know
  3. oldwing

    st90 engine in a ct70

    Might just have to do that, but I have the opportunity to buy a st90 engine complete for a pretty good price, so if it bolted in I'd go for it. An 88cc kit on a 50 or 70 will apparently make more power than a stock 90 and weigh about 15 pounds less but I'm on a really tight budget.
  4. oldwing

    st90 engine in a ct70

    I'm trying to figure out if a st90 engine will bolt in a ct70 frame. I've always assumed the frames were the same so the engine mounts were the same but I read somewhere they might be different. If they are different, how are they different? Upper mount wider? Lower mount spaced further from upper ? I've got a ct70 frame with no engine and was considering buying a st90 engine to put in it.