I was having the same problem with a Branson 2910. The replacement filter was a Napa Gold 51202. The filter on it was probably the original filter since maintenance was not the previous owners strong point. When I put the 51202 the hyd. worked very slow, jerky or not at all if it was cold. The specs on the 51202 were 5 micron and paper filtering media. I looked on the WIX site and found 51205 filter with wire screen filtering 30 micron and 28 to 30 gpm. Put this on and hyd. work as they should. After reading a lot of post it seems some filters might be to tight on filtering with paper media. I do know that 5 microns is very small. Usually things in the 5 and 30 micron would be used in polishing compounds. Hope this helps it was the solution I found to poor hyds. 51205 filter is shorter.