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3660 startup "jump"....

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  • 3660 startup "jump"....

    Ive seen several (older) threads on the motor jumping during startup of the 3650/3660 saw. A lot of people said they have no problems, but Im intermittently having this issue.

    Ive adjusted the belt and pulleys as best as I can tell. All trunion bolts are tight. Even used a spacer to make sure that the motor alignment pins are even while tightening the hex bolts. I still (but not all the time) get a loud and shaky startup. Its not HORRIBLE, but when it starts up smooth its so much nicer.

    Any other suggestions? Im wondering if its just variations in the motor, considering they are using an el cheapo.

  • #2
    Re: 3660 startup "jump"....

    I don't know if this is the same problem, but it sounds liker a belt tensioning issue. Do you know when the problem occurs? In my case, there was not enough belt tension when the blade was in a lowered position, such as one might use to saw 3/4" stock. The saw would squeal and shudder at startup for a few seconds, then kick in to normal operation.

    I followed this procedure and my startup problems went away:
    Excerpted from a previous thread (thanks, GoFor)

    1st: Raise the blade all the way up to its highest position

    2nd,: Pull the motor out until the motor rotates almost all the way up, compressing the spring on the motor mount plate until it is 1/4" from hitting the screw heads. Tighten bolts on the motor mount shafts. (If doing it by yourself, a speed clamp holding the motor up to almost compress the spring may make it easier to keep in place while snugging down the bolts. The 2 shafts on the mount assy should still extend through both sets of holes in the casting. Mine stick out about 1/2"+ beyond the last set of holes)

    3rd: When you squeeze the belt, the motor should move almost the remaining 1/4".

    With the blade all the way up, there should be just enough left in the spring on the plate to allow it to move some. The spring is providing almost all the tension. Spring compression 95%, motor weight 5%).

    With the blade all the way down, the weight of the motor is providing almost all the tension, and the spring on the mount plate is almost fully extended, but not fully all the way. (Motor weight 95%, spring compression 5%)

    The balance between the motor weight and the spring compression is what keeps a constant tension on the belt no matter what height the blade height is set. The rod that extends through the curved slot should not be all the way to the end of the slot at either extreme - blade up or blade down.

    Hope this helps


    • #3
      Re: 3660 startup "jump"....

      Thanks for the tips. It turns out I had not enough tension on the belt (per your procedure), but even after making the motor plate gap smaller, I still get the bump.

      Oddly enough, the first two dead-stop starts I had with it set this way were bump free. Strange that it works sometimes and doesnt work others. Im wondering if it might be something other than belt tension (i.e. starting cap, motor, etc)


      • #4
        Re: 3660 startup "jump"....

        i get a "bump" when i first start mine as well. not sure its the same as what you describe though. it basically just jumps and then quiets down and runs smooth. i thought it was normal