Helen4521 wrote:
Can anyone help please? When I was mowing, I ran over a largish stone.
The mower made a noise like the stone was whizzing around with the
blades then white smoke came out of the exhaust. When I stopped the
mower, I tilted it up (only slightly) to see if the stone was still
underneath, didn't see it but saw score marks where it had been. The
blades still move OK. When I started the mower again, it sounded like
a tin can and there was a bit of oil coming out of the exhaust. Have I
done serious damage? What should I be checking next? The mower is
only 2 years old.

Pull the plug wire, and rotate the blade. Chances are, you will find that the
crankshaft is bent, causing one end of the blade to be higher than the other.