The Oregon Seller's Property Disclosure Statement paragraph 9A is "Full Disclosure By Seller(s) - Are there any other material defects affecting this property or its value that a prospective buyer should know about? If yes, describer the defect on attached sheet and explain the frequency and extent of the problem and any insurance claims, repairs or remediation."
The principle here is contained in the interpretation of ""affecting this property or its value", and for that you'd best be served by a real estate attorney, which I am not. It also asks for the seller to explain the "frequency and extent of the problem".
The problem is that we all probably have a different definition of "occasional". Something that happens once or twice a year might not be material. Something that happens every week probably is. The area in between is why you should consult an attorney.
The general idea of disclosure is that the seller is not to conceal any information that a buyer would consider material. One test might be to put yourself in the buyer's shoes. If you bought this home and nothing is said about dirt bikes or dogs barking, would you feel the seller had not honestly disclosed something material?
The other part worth discussing with an attorney is the question of "remediation". Have you called the authorities to file a nuisance complaint over the noise? Have the neighbors complied?
Finally, it is almost impossible to "over disclose". You protect yourself as a seller if you are honest and complete in your disclosures. If you don't you run the risk of getting a call from the buyer's attorney about a suit claiming that you did not adequately disclose something that is material.
Your need to review all those questions with an attorney specializing in real estate. If you need a recommendation of a good firm, email me.