working on 616 s/n 5117996, I replaced a weak left side hydro (771-125) with a used newer (771-099) from a 618, the replacement motor minus final drive was set up for a remote oil reservoir , so I took the top cap off of the -125 and put it on the -099 since it has the top mounted reservoir and install the bottom plug , I than installed the final drive, reinstalled unit and filled with grasshopper hydro fluid and let the air work out, I started mower and ran hydro forward and reverse for about 1 minute each way , no more air coming out the bleeder but fluid has air bubbles and I have no movement in the final drive ????? help please