86 115hp Oil leak

[Fresno Red]

I've got a good running 1986 115hp that drains oil thru the carbs when the motor is tilted up. Oil comes from the intake of #2 and 4. Have removed oil pump and inspected and it appears to be the check valves are leaking when the oil tank is high enough over the carb ports to drain. Will drain the entire oil tank if left tilted long enough. Suspect I need to replace pump but don't want to if that's not the problem.

Any other ideas? Have a couple weeks before next club tournament.

Thanks

[rodbolt17]

I have heard of folks removing and cleaning the check valves.
I have heard of folks removing the original check valves and installing the later inline check valves.
and they make a kit to convert it from the old kien pump to the later mikuni pump.
your choice I guess.
I never tried the first two options.

[Fresno Red]

Thanks for the reply. I've seen the conversion kit listed. Is that the new pump and is it worth the extra bucks? Is the conversion much more of a task than changing the pump?

[rodbolt17]

the original Kien pump has not been avalible from Yamaha since about 1990/91.
the kit doesn't come with very good to no instructions.
there are some tech bullitens still avalible on the conversion in the YMBS service library.

[Fresno Red]

Some confusion on my part as to which pump is which. On my motor, my pump is like the Yamaha pn 6E5-W1320-00-00. Is that the old or new one? Sorry to pick your brain, but being retired, I don't spend bucks I don't have to.

Thanks again.

[rodbolt17]

if yours has the 4 nipples pointed straight up and NO inline check valves and has KIEN written on it its the original KIEN design.
if it has 4 nipples ,2 on each side and inline check valves and has MIKUNI written on it its the later post 1990 style.
that part number is rather meaningless to me at the house.