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Sector gear & Piston teeth meshing - teeth too tall?

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  • Sector gear & Piston teeth meshing - teeth too tall?

    Hi guys,
    Currently working on a DMR build. Whenever I put the motor in, it locks up. I removed the anti reversal latch but this did not solve the problem.

    Iím my latest removal of everything, I have checked the shimming, no friction on the gears. However when the piston is inserted, it becomes very hard to turn the gears manually, with no main spring installed. With the gearbox half open, the sector gear is actually pushing up into the piston, trying to push it off its tracks. Iíve never heard of this, but is there a different height on teeth in gears? When the gearbox is all together, a pull on the trigger gradually brings the piston back about 3mm at a time. When the motor is removed, the piston and spring are held in place against a 420fps spring!

  • #2
    Narrowed this down a bit. The piston itself seems oversized. Really weird. No spring, no gears, just piston, cylinder, and casing, the piston is nearly stuck in place along the gearbox casing. No signs of damage to either part...


    • #3
      Quite common I have found. The piston rails will need to be sanded down to fit / allow free movement.
      Just be careful not to take too much off so it can rotate, rather than just be free.


      • #4
        Thanks Clot. Never seen or heard of it myself. Weirdly itís a Dytac gearbox, and the piston is the same colour/style as my other Dytac gearbox, which is fine


        • #5
          At least its something basic and straightforward to rectify, either sand down or replace

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          • #6
            Well, with that done, now the cut off lever only allows for full auto or safe. Doesnít seem to be engaging the trigger contacts. I have w feeling this Ďfully workingí gearbox I was sold was made out of random parts.


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            Boo-Sabum Ben Instructor & Umpire with the International Taekwon-Do Federation Find out more about Boo-Sabum Ben