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Instructions for assembling OS 105HZ engines.
  1. Assemble the connecting rod wrist pin to the piston, ensure correct orientation. Lightly oil the pin before assembly.
  2. Lightly oil the piton ring groove.
  3. Carefully roll the piston ring into place and locate the gap in line with the ring retaining pin.
  4. Carefully mark the top of the piston with a pencil to show where the ring retaining pin is fitted.
  5. Fit the piston rod assembly into the engine ensuring that the piston and rod are correctly orientated.
  6. Lightly oil the cylinder inside and out.
  7. Push the piston to TDC and ensure that the ring gap is in line with the retaining pin.
  8. Line up the cylinder locating groove with the liner locating pin in the crankcase.
  9. Carefully slide the cylinder onto the piston and into the crankcase watch to see that the ring collapses down with the gap in line with the mark on the top of the piston. DO NOT ROTATE THE CYLINDER once the ring is inside the cylinder.
  10. Slide the cylinder into the case, if the radial location is not correct you can gently rotate the cylinder at the same time as moving the piston up and down the bore.
  11. Fitting the Cylinder Head - When fitting the cylinder head line up the bolt holes with the tapped holes in the crankcase before locating the head onto the cylinder, do not rotate the cylinder head after it has been located onto the top of the cylinder as doing so can break the liner locating pin.