last friday I rode home to South Bohemia, stopped at gas station and noticed oil light on idle. Shut off the engine, cleaned up all the contacts, the oil sensor - no use. Light stayed on on idle and slowly dimmed in higher revs. No use. Towed the bike home in a van and started to dismount the oil pan and etc. Friend who is a Guzzi experienced mechanician helped me. Firstly we measured the pressure of the oil. ZERO on idle and 1 atm in 2500rpm. Hm. So we took down the oil pan and cleaned the valve that regulates oil pressure in the engine. It worked fine. Hm. After hours of playing, we took down the oil filter (UFI) and finally found, the rubber seal ring on top of filter was broken, closer inspection showed it has been rotten by some kind, the surface was porous.
so filter was replaced and pressure is now 70 PSI on idle. Great!
better watch those UFIs now