Originally Posted by earlwb

If i remember correctly, I have to look it up, the Fox Butterfly carbs came in two or three venturi bore sizes for the 40's (45's) and the .60s, the old .78 might have had a different bore too. The MK-X carbs had four different bores and a Fifth Q500 carb that was bored out even more. The EZ carb had two bore sizes, one for the 45's and one for the 60's and 74 engines. With the latest TN carbs, I assume they had two different bore sizes for the .45's and the .60/.74 engines.

Ok looking at my notes.
The .40 and .45 engines had a carb with a .290 to .312 bore depending on the production run down over the years

The Fox Eagle II, III and IV .60and .74 engines had a MK-X carb with a .330 bore. The Fox Hawk .60 and Eagle I .60 when sent in for servicing had the MK-X B carb put on with a bore of .312 size.

There was a MK-X F carb with a .350 bore for tuned pipes too.

I think that the EZ carb had a .312 bore for the .45 engines and a .330 bore for the .60 and .74 engines.

The Quickie 500 .40 engines had carbs with bores of .350, .360 and even .375 depending on the production run at the time. One could put the MK-X A type carb with a bore of .290 and it became a Sport Quickie if I remember right. it would then idle fairly well.