Sounds to me like shes nipped up in the bore possibly to a broken ring or lack of oil or coolant unfortunately the damage is done you will have to remove the cylinder head & barrell to determine how much check the oil pump for blockage & function was there adequate oil in the tank alsowas the coolant resevior full at the least it will need a set of rings & the cylinder honed at worst big end bearings if the bottom ends locked up this involves splitting the cases so for your sake I hope my initial diagnoses is corrrect