Lorenzo, No I was referring to the older zinc body Mikuni side/bottom main jet

(my preference) carb,24mm dia. which have found as a good Amal replacement.

Larry

My Bultaco Sherpa 250 1968 had a amal concentric on it but my pals 1967 5speed had an IRZ as on the 4speed the body was prone to wear as was the slide these were made to a price and suffered a bit in wear

Edited December 11, 201411 yr by naichuff

They were a 24mm IRZ , hard to get parts for now ,

After a bit of messing , I ended up going up 1 size on the main and up to a 40 on the pilot which is standard (I thought it was 20) and with the needle clip in the middle position and roughly 2 turns out on the air screw , bike is now bang on with no pinking , thanks for all the suggestions