My brother let me hang onto his 97 Ducati Monster 750 that has been sitting most of the winter. Every time I start it after sitting a week or more, the oil light stays on for 20-30 secs before going out. Once warm, the pressure looks normal, about 30psi at idle and 65 to 70psi when revved. I'm wondering if this indicates a relief valve issue or perhaps a problem with the pickup. Is there a reliable way to clean and service the valve without replacing it outright?