Your engine seems to be OK but has some problem that allows it to
oscillate, some ideas:
The engine should idle at 750 rpm, the idle stop set screw is between
the injection pump and the block. A deep socket and large flat blade
screw driver is needed to adjust it. I suggest a one turn (clockwise)
adjustment to raise your engine's idle to say, 750 to 800 rpm. It's not
an exact science. Write down the adjustment so you can reverse it if
The rack damper pin or screw is spring loaded and stabilizes the fuel
rack. Otherwise, the rack picks up the engine's oscillations and that
causes the engine's speed to oscillate - which makes the shaking worse.
There's a "new" version of this pin which has a stiffer spring, about
The rack damper adjustment has two limits: Too tight will cause the
engine to stall, too loose will allow the idle to wander so low to stall
the engine when hot. That happened to me.
These engines also have a small shock absorber on their left and right
motor mount, does yours?
The left and right motor mount pads are NOT interchangeable, one is
designed to be compressed, the other pulled by the engine's torque. I
hope yours are correct.