Got a 64 122 with the B-18D. Front carb hangs slightly returning to idle. A slight nudge with the thumb and it rolls right on down. Springs are good. The bellcrank seems slightly loose with 2 or 3 degrees of free play. Flats on the throttle shaft look very slightly rounded. I tried tightening the fastening nut but if I torque it too much the throttle binds even more. There seems to be a fine line between loose and too tight. Bushing wear seems not to be a problem... I tried the old Berryman trick to sniff out air leaks and all seems to be tight.

Would ya say the next step is to take the carb apart and physically check for shaft wear??

The end play of the throttle shaft should have a side-to-side movement of ~.03 in, and any excess play should be taken up with thin flat washers. It sounds like the washers and/or the location of the throttle plate is not right. As mentioned below, loosten the throttle plate screws slightly, but before tightneing, run the throttle shaft side-to-side to center the plate and shaft in the throat of the carb. This should give the same shaft width extending beyond the carb body on both sides to where the nut stops when fully tightened. If the washer thickenss is correct, the nut should be fully tightened without any binding at all. Before you reassemble the nut/shaft, put a gob of high viscosity Silicone stop-cock grease into the bushing holes. This will give it a nice leak free seal.
You may have just run into the throttle plate loostening up and needs re-centering.
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'89 245 Sportwagon, '04 V70 2.5T Sportwagon

Thanks guys.... That is too easy!!!! Gravity strikes again!!!

Based on the geometry doesn't take much wear I guess.

Check that the butterflys are not binding in the throats. Look for scoring inside the throat.

If it is, then slightly loosen the two small screws holding the buttfly to the shaft, force the butterfly closed by turning the shaft, then tighten screws. This should center the butterfly. Don't back the screws out too much as they are supposed to have a buggered up end, once installed, to keep them from backing out.

Good luck.

ml
67 122 wagon
79 mgb

Shaft wear allows the shaft to drop slightly, which causes binding of the valve against the carb throat. A little recentering might delay the inevitable rebuild.
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I'm JohnMc, and I approved this message.