Hi everyone,
I'm running into a wall on trying to get my O290D2 running correctly. I purchased a rebuilt carb 10-3565-1 from ACS a while back and just now have gotten around to installing it. The engine previously was installed on my PA22 and ran fine back then, with the old carb. I just installed the engine with rebuilt carb on my Cub.

The problem I am having is I cannot get the engine to run between 1100rpm and 1500rpm for more than a few seconds without it surging and cutting out, like its running out of fuel. It runs fine at idle and runs perfect from 1500rpm to WOT. Just the midrange is not working.

I found that if I enrichen the idle mixture about 4 turns and apply full carb heat, the engine will run OK at the midrange rpm.

I've done all the normal checks for intake leaks and verified no fuel obstructions. All the screens are clean.

I suspect something wrong with the Carb but before I get ahold of MSA customer support I thought I would ask the smart folks here. Maybe I am missing something?

Thanks, Scott