I am not an expert on it, but I believe the solenoid opens the pump to full open for a specified short period of time on startup (like 5-10 seconds). An excess of oil should NOT lead to seizure, but it sure would fiddle with your plug chops and give you confusing readings.

Disconnect your oil pump solenoid and see if that does anything. If it doesnt, maybe the solenoid is internally stuck.

If you need one, I do believe I have a good one laying around in my stash here somewhere. Can you give me solid tips on registering an NSR here? Thats all I would ask in payment...
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Paul Herr
'88 FZR4/GSXR/YZF Frankenbike
MY BIKE PICS