Kobelco sk120lc bucket won't curl!

I recently bought a Kobelco sk120lc mark IV to use on my farm, I have experiance with all types of heavy machinery and bought this machine knowing the bucket cylinder was in need of rebuilding as it had no digging power. I rebuilt the cylinder even though I found no seals that were obviously wore or damaged and put back together with the problem still unsolved. Bucket has plenty of pressure on dumping side and all other hydrauiocs are good.