I just pulled a spare 1405 (or was it a 1406?
) off the shelf.
A 0.028" drill bit is the biggest that will fit in the orifice. I'm also having an off idle stumble, so I may just drill them out to 0.035"
the 1405 that i'm using for a secondary carb on a ch28 did have a .028" idle jet and the 1406 i use for primary had a .033" idle jet. ironically these two carbs were totally different internally in relation to the clusters and jets. i'm using .036" idle jetting now in both carbs but i do have a little bit of cam in the engine and sometimes that needs a little fuel help. i use nothing bigger than .028" squirters with the orange/tan ( 1467 pump) accelerator pump (carbs came with this pump) and no stumble, hesitations, spits, sputters or nothing adverse. power is very smooth and reliable.
