Carb issue?

Sometimes when i am cruising and when coasting down to about 20-30 mph or so i press the throttle again (gently) to speed up and there is a dead spot, just a second or less and then it picks up again. What could that be?

Thanks.
Robbie

 

Accelerator pump possibly?

 

Thanks!

 

The power piston spring is probably getting a little weak. I'd pull it apart and give it a little stretch

 

Thanks. Will check. I've never removed and checked the accelerator pump before.

 

The power piston is a separate deal from the accelerator pump. Its the enrichment circuit on the primary side. The spring must overcome the vacuum signal and lift the rods out of the jets. When the spring gets weak the carb will develop a good hiccup

 

Ofcourse, i was thinking about the accelerator pump. I know it's another part in the carb. Thanks again.

 

Applying light throttle and light engine load very slowly is usually a tad lean for calibration. The PP or spring isn't a player with light engine load unless you are depressing the throttle hard and quick enough to have vacuum falling off pretty far.

Same with the accl pump, it does little to nothing slowly applying the throttle and very light engine load. Any quick or quick/heavy throttle movements the accl pump is a HUGE player in preventing a momentary lean condition or stumble/hesitation/bog....

 

Thanks. I found one spark plug which had a crack in the porcelain which caused a misfire. Throttle response is back to flawless

 

Not surprised, most of the "carburetor issues" I'm asked to help out with on vehicles brought here for custom tuning are "distributor/ignition issues" instead......