After adjusting the intake and exhaust valves on a b&s 18.5 ohv the intake valve works fine. The exhaust valve can't do the whole cycle without bottoming out. Does this mean the lobe on the cam is worn, which would make it to tide while setting it on 1/4 past dhc. When I back up the rocker adjustment so that the valve actually works, the rocker will be so loose that it actually comes of when not compressed.

Hi,
The best thing to do is set each to 0.006" at 1/4" past TDC on the compression stroke and then turn the engine through manually. The movement of the roccker arms should be virtually the same though at different times. There were some bad camshafts out there and the exhaust arm will move noticeably less than the intake. There have also been cases where the stud that the rocker arm fastens to has come loose and backed out.
Peace,
Clarke