Hello everyone, new to the forum...

I need help with my 2006 yamaha FXHO. I just put in a new sbt engine and is throwing a oil pressure light. this problem is weird as it will only throw the light at first start up when the engine is cold. I will shut the ski off and start it right back up and the light will not come on for the rest of the day no matter how much I ride. I soon as it has cooled down completely mainly the next day, I will restart the engine and light will pop back on. I have tried to replace oil filter thinking valve was bad and also the oil pressure sending unit with no luck. I was told that the ecu does not even monitor the oil pressure sensor until the engine goes above 2500rpm because they run real low pressure at idle.

I cannot find anybody that has had this problem before. Does somebody have a repair manual they can email me or shed some light on this?
I was thinking possible bad ecu?