Hi. I have a recently purchased 1998EV Cali, sump with extension. I did not notice an oil warning light on when I first rode it. I have changed the oil and filter carefully and blown through sump oil ways as best I can without an airline. Everything very clean and correct I think. Result: warning lamp only goes out after approx.3700revs. I have fitted a new oil pressure switch but to no avail. The bike seems to be running well. I have now done about 230 miles and it hasn’t seized up yet! The filter now fitted is the same as the previous one. I can’t imagine that taking the sump off again is going to reveal anything but…?
Oil pressure release valve ?
(Also in the sump)
would double check the gaskets either side of the sump spacer around the oil pick up area
So it was alright. Then you changed the oil and filter and it wasn’t. You’ve replaced the oil pressure sender and it is no better … ?
I’d be going back in.
Thanks. You’re right of course (groan). Sump’s coming off again…
It gets easier with practice,
stick it on the centre stand and drop the oil use a scissor Jack to support the sump, (4 middle bolts out first), undo the outer ones lower, sort it out and refit in the reverse order, 
Before you remove the sump I would put a pressure gauge where the sender is, I use flexible pressure gauge kit. It tells you instantly what the pressure is think from memory it’s 4 bar if you look on HMB site they sell improved pressure relief valves set at ? ( 4 bar ). I have recently removed the filter on a Millie and it was not tight enough in my opinion. Think the circuit is draw oil through the strainer into pump , to filter , through filter splits two ways one way pressure relief valve ( controls both sides) to mains, cam , sensor etc. Note the pump is driven by a gear on a shaft tapered with small key loosing drive would give same symptoms. Happy to respond to pm
Regards Ratt
Many thanks for the replies. And now it’s time for the VERY RED FACE! Despite what I thought was a very careful assembly, I had put the sump extension on upside down. Well, the lighting conditions weren’t too good at the time (lame excuse). That pressure was reached at approaching 4000 rpm is intriguing though.
Good to hear that you’ve got it sorted