Z-Force 50 hydrostat problems
 

I just bought a 2007, Z-force 50. The motor starts okay but the left hydrostat seems very week compared to the right. The mower will turn to the left all day but really struggles to turn to the right. I have a new hydrostat belt ordered. Last weekend I replaced both hydraulic filters and drained the old hydraulic fluid. The old fluid was a nasty milky, chunky color so who knows the last time it was changed. I added new hydraulic fluid, 20w-50, tried to bleed the system by driving forward and reverse several times but the left side hydrostat still barely moves. Does anyone have any suggestions?

Model # 17AH3AGP709
Serial # 2D247Z02026