Surging Briggs

[PTmowerMech]

Model # 13R2320021FG1

It's surging, unless I choke it about 2/3rds. I cleaned the carb. Which wasn't bad, that I could see. There was a little trash in the bottom of the bowl that had been sitting.. Also a little more in the shut off that's built onto this carb.
The pilot jet wasn't clear, so I reamed it with my E string, but couldn't get the B sting through. So messed with it til I finally just broke down and drilled it out with the next size up from the bit that fit. (tiny bits that come in a set.)

Put it all back together and it still surges. Just not quite as bad. And I only have to choke it about 1/2 way. I don't feel comfortable drilling that pilot out any further, without asking you pro's. Those jets are tiny for a reason.

So the question is, how much is too much (ID of the jet). And what else could be causing it? The mounting gasket is good. Inside the tank looks new. It had a 1/4 tank of gas, that smelled just a little old, but not too bad. I topped it off with fresh gas.

Also this splitter looks newish, and it's rarely been used. My dentist owns it.

 

[PTmowerMech]

42 replies and no suggestion. So I stepped up another size, then another, then another. And it's running smooth now. My cheapo calipers only go 2 digits passed the decimal. But it said .03. The one size lower also read .03. So I'm guessing it was .035.