honda 400ex help wont take quick rev bogs rich or lean?

[Daniel]

hello i recently bough a used 400ex its got fmf pipe air box lid removed and choke removed it wont take a quick rev when i let the engine die down and the gun the throttle but it take the revs when i twist the throttle easy any help would be apprenticed by they way its seems to runs hot aswell i use 10w40 oil