First start!

[Greaser Greg]

 Ahh, so... Thank you very much! 
Do you measure the piston spring for spec length, or does the oil output tell the tale?

[SUPERTUNE]

Sorry, not understanding what your referring to...
The check valve springs that hold the one way ball valves?
C

[rd400canuck]

ok... turns out there is no leak. It was the oil feed hose out of round. The hose is so old it is no longer pliable and wouldnt form a tight seal allowing oil to seep past.

However... there are still air bubbles in one of the lines that show up each pump so I have ordered a rebuild kit from economy cycle.

[Greaser Greg]

Sorry, not understanding what your referring to...
The check valve springs that hold the one way ball valves?
C

No, the one spring in the upper part of pump that returns the plunger to lower detents on distributor shaft cam.
Sorry, no diagram available to me on this iPad. It's #10 on exploded view if you have that.

[SoCal250]

If you're having issues with old hoses I would replace with new. I've seen the hoses from the pump fail, and on my bike a few years ago I had the main supply line from the oil tank spontaneously split lengthwise from age and spit oil on my rear tire.

OEM hose is still available from Yamaha. (These are black hose BTW).
Oil lines going from the pump to the carbs, 2 required. About $5 ea. After trimming to fit you will have some left over because each part is 27.5" long.
90445-05M07-00

Also a good idea to replace the small metal hose clips, 4 required. Economy has these.
90468-02033-00

Supply line going from oil tank to pump
90445-09122-00
When installing make sure that the fixed ring on the outside of the hose is closest to the tank. This is used to capture the spring and hold it in place.