Honda BF 250 Lucky strike2

[lucky strike2]

My oil pressure green light starts to flicker erratically after about 10 min running at around 4500 rpm then if you drop down to around 3800rpm the light stays on and the alarm goes continueously and the motor goes into limp mode. swith off the motor and restart it will run fine up to 2800 rpm move to 3800rpm the same senario. however if you move fast through 3800rpm to about 4800rpm then the green light flickers erratically and no alarm and no engin into limp mode.
I have changed oil and filter
swopped the ecu box
checked the igniting wiring
run dr H and it showa no sensor error
the motor has less than 400 hours

I have now run out of ideas. any help as to where from here. My next step is to chaange the oil pressure sensor

 

[mlf]

have u found the problem yet?