The site you're dealing with, I remember the site owner when he 1st started it back in 06 or 07, he used the handle Doc Gear on the garden, he wrote near perfect english.
The squish collars may not be necessary right now on the double barb nipples with the low working press you currently have, but over time with the constant flex of the rubber hose with the changing pressure may pop a hose off & create another ugly mess to clean up.
Along with the use of mini shop towels (toliet paper
) I use Q tips as well to soak up oil from tight areas, and Q tips soaked with thinner to wash away the oil film as much as possible. But still it'll collect dirt & fine dust... ocassional use of pressured air cleaning & hopefully no grit get's packed in an area to cause binding of a valve.
All my hyd models have been converted to variable speed with no leak problems, but I have used the oem supplied motors for the pump. Do you have any idea how fast your motor swap is spinning? Perhaps you could be pushing the oil too hard.
I've had troubles with leaky cyls out of the box, but never a new valve... not to say it couldn't happen... the tolerances wouldn't have to be off by much with the plunger rod & valve bore, and the possiblity of a nicked o ring during assemebly too... I wonder how many pumps, valves, cyls Leimbach makes in a yr for the world market... you see their stuff everywhere! I heard yrs ago that it was just a father & son working in a small shop... the ol man must be just about 65 now.