I left my snowmobile on another's property with permission and they sold parts off of it without my consent, what can I do?

You can file a lawsuit for conversion against those who removed and/or sold the parts of your snowmobile.  Your damages (the amount you are seeking to recover) would be based on the cost of repairs (replacement cost of the parts) or diminution in value of the snowmobile due to the missing parts. If the property owner removed and/or sold the parts, that individual would be liable for conversion.  If the property owner did not remove and/or sell the parts, that individual may be liable for negligence since this occurred on his/her property without adequate safeguards for the security of the snowmobile.