RE: O S 91 BRAKE IN ??
NO, not unless you are getting the idle too low, about just before it is going to quit on you. After the ring starts to seat you can begin adjusting the needles. My .91s just tick over, idle is said to be about 2000 but they will go a lot lower. You can check the valve adjustment just to make sure they are set then set the high and low end so the engine runs smooth all the way from the low to high. Not real sure what Hammered Hard means but they will run hard if they are running too slow.