I am trying to find the true size of a 300ex carb ,The clymer manual says a 250x and the 300ex have the same size carb a 29mm. My manual only goes to 1993 to 1996 300ex . But if you check out a newer 300ex specs it lists a 32mm carb . Did they change the size of the carbs ? If so what year did they change ?

 

I measured my 400ex carb and on the engine side that goes into the carb boot is 1 3/4 outside and 1 1/2 inside which converts to a 38mm . I had this carb on my 350x motor and it seems to be too much carb for the motor . I had an old 250x carb laying around and I changed the jets to the same as a stock 350x and the bike runs alot better. If someone has an old 300ex carb laying around I want to check the size of the carb going into the carb boot( inside measurement ) I believe the 250x and the 300ex is the same size but I would like to make sure . I read other posts that say the 300ex has a 28mm carb thats quit a big difference . I am just curious what the size is . Everyone says a 350x stock carb is a 34mm but I have an old 3 wheel action magazine that has the 350x first debut and it says the 350x has a 31mm carb . So I would also like to get a measurement for a 350x carb thanks Bob

 

stock 350x is 31mm

 

thanks sdm111 .

 

I just bought a 350x carb on ebay . Its a junk carb but I just wanted to measure it . A 350x has a 1' 5/16 opening making it a almost a 34 mm it was like 33.3445 . I know a 400ex is an 1' 1/2 38mm

 

A carb is measured at the venturi... not the ends.