David P: Earlier Post to Aaron Ford

Your comments To Aaron Ford below have raised a question about what I discovered when I recently rebuilt the pump in one of my MF-35s. Specifically, upon reassembly of my pump using aftermarket TISCO parts, I discovered that the piston assemblies interfered with the linkage for the oscillator and the pump would not rotate a full 360 degrees. I made several attempts to reorient the piston assemblies but could find no arrangement that eliminated the interference. Eventually, I relieved the corners of two of the square piston frames with a die grinder, reassembled the pump, installed it in the tractor, and everything seems to be fine.

Annoyed with TISCO, I attributed the interference to an aftermarket redesign of the piston assemblies without proper verification that the redesigned parts would not interfere.

The assemblies are installed such that a machined surface of each is toward either end frame of the pump. According to my I&T manual this is correct. Unfortunately, when orienting the assemblies this way, the factory relieved corners of the piston assemblies are not in proper position to provide clearence for the oscillator linkage. Orienting the piston assemblies such that the unmachined surfaces are toward the pump end frames would result in clearance for the oscillator linkage as the pistom frames are relieved in this area.

Have you seen this before? Additionally, you state that the pistons are not centered symetrically on the square frames. Is this offset side to side or vertically? The original pistons appear to be symetrical and I cannot look at the new ones as they are in the tractor.

I am contemplating removing my pump again to see if perhaps I missed something. Perhaps the piston assemblies are upside down causing the interference.

Any advice that you may offer will be appreciated.

Dean

Thanks for your reply. Clearances and rotation of the pump appear to be fine. My concern has to do with the need to grind reliefs into the corner of the piston frames to provide clearance for the oscillator linkage. Having done this, everything seems fine but before I did the piston frames would interfere with the oscillator linkage preventing the pump from rotating 360 degrees.

It just seems odd that I should need to do this with the new pistons but I could find no orientation that would allow full rotation until I did.

Are the pistons centered on the frames vertically? If so, assembling the pump with the piston frames upside down might cause this. Otherwise, someone must have missed something when redesigning the TISCO piston frames. The replacement piston frames are noticeably different than the original ones.

Thanks, again.

Dean