Thanks cepx - someone mentioned polishing the piston and bore in the pump and then no worries.
Correct. If you free it up enough. You said something else that caused bells to go off in my head though.
Guess some crude or heat from brazing the pick-up caused this.....
You bet it will. Find out what size the bore where the piston goes is and get a flat bottom reamer and ream it by hand to clean the slight warp out of it. That is probaly whaty happened it probably warped the cylinder. If you can't find the size make it .003 to .005 bigger than the piston. You need the piston to float free and to not stick even if jammed hard toward the bottom.
TRASH THT FACTORY ADAPTER and buy a Billet Aluminum one from Moroso, Canton, CV Products, B&B or someone. The factory adapter is paper thin in it's weak places.
Ed