Ran good all summer, then randomly started bogging when i gave it throttle and ran as if lean, and backfired alot. so i cleaned all the jets, and the acc. pump worked properly. still ran horrible. enrichened the fuel screw about 2 turns, no help. so i looked up the issue on this forum. i then checked the valve clearances, all were to tight, re shimmed, no help. then took offthe mufflers end cap, there was no packing at al, repacked it.. nothing. then took the carb apart again, saw that the acc. pump diaghram was torn, replaced it. the bike was now fixed, ran way better than ever. then a couple days later, running lean again, i enrichened the fuel screw, it fixed it for a couple minutes, enrichened more, ran great again for a couple minutes, but kept going lean. so i thouroghly cleaned the carb again, nothing. so i put the needle to a more rich setting (two notches down on the needle). no help. i did check the exhaust for leaks and the intake boot, and the hot start crap, no leaks. im completely out of ideas, other than jetting. any help would be greatly appreciated.