Test the muffler/ tuned pipe pressure fitting for restriction. A fuel line restriction like a kink, dirt, too small a line, bad in-line filter or filter-clunk. A fuel tank that's too low can cause problems. loose the fuel-er valve if you have one.
PS, If you can't keep bearings in that 50 SX, scrap it, the case bearing bores had bad alignment in many of those.
Last edited by freakingfast; 10-06-2013 at 07:00 PM.