I changed the magneto on my Honda GX160 QX2 5.5hp. small engine and I still have no spark. Any suggestions on what to check ?

There could be an issue with the oil sending unit, spark plug boot or faulty on/off switch. Easy tests. Always use a new plug for testing. Unplug the oil sending unit wire and retest for spark. If spark may need to change the oil or low oil. If still no spark, leave the sending unit wire unplugged and remove the boot from the plug wire. Insert a short piece of paper clip wire into the end of the plug wire and hold near metal of the engine for test. If spark, replace boot. If still no spark, unplug wire from on/off switch and retest. If still no spark suspect faulty coil ~ redo all tests using old coil. If still no joy return new coil for exchange. I use a growler to test coils(growler used for testing armature for short, place one leg of coil on each pad of growler and activate growler for short burst). Good luck.