i put a pipe on a very nice rebuilt a3 87 golden bullett, the pipe on the stock engine sounded great, better low end and more top end, it smoked my stock e 50 off the line and on top end. do it. jetting , it has been a few months and i sold the bike but, think i had a 53/ 54 with the air box, and maybe a 57 with the del puck and no air box.
ran great do it, we put a k star on it also and that stepped up the game for sure, shorten the spring a bit on the second gear just a loop or or 2 and cut some slits in the pad and it will engage even better stock pipe / kit or n pipe/ kit