Yup, unbalanced carbs.

Heres the lowdown -- you MUST adjust the carbs to pull the same amount of air. This is supposing you have a good engine and proper valve adjustment, etc.

Unhook the link between the carbs and set basic throttle position to exactly the same opening on both carbs. You can use your flow meter or just block the air bleed and check speed drop, either works, but if you have a decent meter, it helps.

Your front carb has the throttle plate too far closed at idle, the rear is too far open.

Once you get that set, you must get the idle mixture set correctly on BOTH carbs. Blocking the idle air orifice must give the same idle speed change on both carbs.

Idle speed must be set equally on both carbs -- turn the screw EXACTLY the same amount on each. Your flow meter will come in handy here, too. I believe the idle speed adjuster is a vertical screw/nut combination on those carbs, but I'm not sure, dont' have a manual any more.

Re-install the link between the carbs so that it fits without pulling either way (otherwise the front carb will be off).

This should get you bad up and running.

Peter

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1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!