Accelerator pump, factory setting?

[rjcthree]

Having gone through the Ellison to MA4 challenge, when I had the MA4 core OH, it came back with the accelerator pump linkage set to the most volume. I get a modest but repeatable stumble when I roll into the throttle, seemingly right at 1500 rpm. It’s most notable when at 1200rpm in the pattern and having to roll into it to adjust. Like Paul’s video, in its current state, it will shoot fuel across the hanger. I’m curious as to where the the accelerator pumps are set from the factory? Next oil change I’ll probably take it to the middle hole, but for right now, I’m gathering data. I admit my idle circuit may be slightest bit lean, but boy are my plugs clean!

otherwise, things are great.

 

[BH1166]

I have two ma4spa carbs. one is 2 year old new , and another same but recently rebuilt and reflowed. Both are set like this. Good luck.

 

[Scott Hersha]

All of mine have always stumbled a bit in that same general RPM range on acceleration, unless you increase power slowly and smoothly. Once above ~1500, I can shove the throttle full much more quickly with no problem.

 

[rjcthree]

Thanks Butch. Scott, I operate similar to as you describe, 1800 being my break point. I’ll dive into the manual too.