In my opinion, I think that most people take the oil pump off for the wrong reasons. I Think oil pumps are great because they feed the correct mixture to the engine at all RPM. If it has been rebuilt before, check the cylinder is not a steel bore or a re-nickalsil. Because, after doing hundreds of the 1200 & 800 yamaha motors, I truly believe only a genuine yamaha barrel with a sized matched pistons are the best option. If it is a steel bore, the carbs will need to be re-jetted along with a bigger needle and seat. If it is a re-nickalsil, well in my opinion they are just a waste of money. If it is a genuine OEM barrel and piston, check the piston and barrel to see why it is failing. Do you know how to read a blown piston?