On my Case 646 with the boom lift control lever, lowering it I can lower the boom gently or fast or push it all the way forward to let it drift down. But lifting or raising the boom, if I try to gently pull lever to lift slowly, it will work engine and or stall it out. I can only pull it back all the way and then it will lift normally (fast)without working engine. Am I suppose to be able to lift slowly without working the engine? If so, suggestion of the problem?