37.5 pilots ?

Hello!
I recently bought a 1978 KZ 650 SR,cleaned the carbs etc., so the bike runs well except for a pronounced stumble at low rpm s.The pilot jets in the carbs are #37.5 while the stock jets I ordered are #15.The only difference between them is that the #15 jets have holes in the tube part and the old 37.5 s don't. Knowing that the P.O. screwed around with the carbs, do those sizes make sense? Are the #37.5 s the right size for air screw carbs and the #15 s for pilot mixture type carbs?
Please help me!

Wow! This is kind of confusing. #37.5 pilots are a common size for a CV style Mikuni carb (BS32/34) but these pilots won't fit a round slide carb which will use a #15 pilot as the stock size. Is there any chance you took out #17.5 pilot jets? ALL 78 Mikuni VM24 carbs came stock with #15 pilots. The stumble you feel is likely that the air/fuel mixture in the pilot circuit is not adjusted properly. #17.5 pilots are a pretty good choice for most any application as the stock #15 pilots are on the lean side. The #17.5 pilots start easier and allow the bike to warm up easier. The pilots needed for your application should be type VM22/210 and not BS30/96 as used in the BS series Mikuni carbs.