I'm running that very same pump Lars with no problems, mind you mines a 4862 for BB's. The bodies are the same just the pumping arm is different. Doesn't make any sense that your's is leaking and I gather it's new. Is there a chance in hell that the eccentric on the end of your cam is the wrong size (to big) and you're bottoming out the pumping arm which will then try to seperate that bolted flange on the pump.
Terry
