I've just got the stock carb on a '70 521 and I'm wondering if anyone can give me a few tips on getting the carb adjusted close to stock or a decent setting for fuel mileage. Right now it seems to be running rich and I've tried playing with the throttle and idle mixture adjustments but without a CO meter it seems to be a hit and miss. Any other adjustments I can make on it?

Perhaps the fuel level is too high.  Needle valve leaking or float sinking.