The Perry carb and the K&B "Ribbed" carb are the same in metering concept, but different in executiion.

The Perry has the metering slit next to the fuel inlet nipple, where the least bit of trash can clog or restrict the flow immediately.

The K&B version runs the fuel through a similar inlet chamber, but the fuel goes past the main needle before reaching the metering slit, which is moved inside the spraybar in the venturi. This isolates it a little better from trash in the fuel.

With either carb DO NOT use anything hard to clean the slit, enlarge it and you've ruined the carb until you get a replacement part. Use a piece of paper or card stock to wipe it out and be sure it's clear, nothing else.

Pictures are first, the Perry metering disc. The slit goes to either side of the hole visible in the relief between the o-rings. Second is the K&B version, the slit can be seen near the end of the tubular extension.

Bill.