Obviously, this owner is serious about not wanting people to trespass. In some areas, a “No Trespassing” sign, especially a “Posted” sign, is held sacred and if taken to court and the owner has the upper hand.
However, there is also the concept of customary or established use. There are cases where an implied easement, or right to pass, is created by habitual use. If others have been using the trail for years, that use could arguably be considered valid for having created an implied easement for the public to use the trail for recreation. There are cases where there is actually a written easement that the landowner is not disclosing to the public. This is certainly true on waterways, where the public may have recreational use of a body of water even if you have a dock there. There may be wording on the owner’s deed that shows existing easements, such as for the power company to enter to check their meter. In fact, since property titles are public information, you may want to check in your county recorder’s office to see whether an actual written easement is listed on the deed for public use of the trail.
If the owner intentionally put up an obstruction – a dangerous object – knowing that it could cause harm, there are other issues at work here and the matter gets more complicated. If the owner is aware of a customary use, he could be sued for a malicious action, especially if the dangerous object was not clearly visible. But be prepared for the owner’s insurance carrier to be unwilling to cover your damages if in fact you trespassed on private property.
The best thing would be to seek the advice of an attorney who is experienced in motorcycle cases to discuss the pros and cons of your case at a reasonable rate.