Someone had installed a big 50cc accelerator pump on the primary side, probably to crutch the missing power valve (PV). With the proper PV installed, it would supply too much fuel on WOT transition. Note the thicker 50cc pump diaphragm housing (A) compared to the thin 30cc part (B)&mdash;a &ldquo;50cc pump arm&rdquo; only pumps 50cc with the thick unit plus a brown pump cam.