my first post so i hope its in the right place, i picked up a lister SR2 a few months back it was originaly hooked to a generator for a loging camp. i had it running and ran pretty good considering the govoner was stuck.   i am trying to find the year of it but the serial number plate is missing, i read that the numbers on the flywheel may have the code also. on the edge of the ring containing the cooling blades  i found 51 85 SR2 18.  could they possibly be the code?