- Jan 12, 2019
https://amalcarb.co.uk/main-jet-size-200.html "The number e.g. 100 indicates that it will flow 100cc`s of fuel in one minute at a specified head. "Interesting discussion. I have just acquired a 1972 750 with a Combat engine. It has been sitting neglected for a number of years and I am just beginning the process of bring it back to life. I am rebuilding the Amal 932 carbs and I find that the have 200 size main jets and 107 size needle jets. The bike is an "S" model with side pipes and reverse cone mufflers and it had a K&N air filter on it when I got it. The needles were in the middle position. Any idea why the main jets were so much smaller than stock? Please enlighten me as I am rather ignorant about carburetor jet sizes. I assume that a size 200 main is smaller than a size 230 or 240. Any ideas what the number refer to? Likewise that 107 needle jets that I have are most likely slightly larger than the 106 jets mentioned above.
107 Needle jets were spec'd for 1970.
200 Mains sound small, more so with 10% Ethanol. But if the plugs look good...