Why wont my lawn mower crank ?

watch it with all that oil!! if it doesn't NEED oil ,, DON'T add any just to try and start it,, that is the wrong way to do it!!!!! check the oil and if there is too much remove some.... then to fix your problem,,, since you said you noticed smoke coming out you may have hit something and broke the shear pin!! this may allow the machine to get out of tune and the valves will not be opening and closing in proper sequence,,, you have to take of the rope coil y and then the fin and magnet y.. on the shaft you should see a groove,, and in the hole in the fin head,,,this is where the shear pin goes,, check yours when you take it apart and see if its been cut...other wise the blade may have been twisted on the shaft,, just a little and this could also affect the timing!!