what does a YB-2A carb go on

Does anyone know what a YB-2A 240460 carburetor was used on. My uncle was trying to use it on his Kohler 3A21 4 cyl light plant but it would only idle and not come up to speed (1800 rpm). Just thought if I knew what it was normaly used on I could determine if it was too small. The Kohler has a 3/4 " manifold inlet and this carb is about 9/16. I guess it could also be a dirty or undersize hs jet. Also, if the hs jet is too small, can it be drilled out or is that a bad idea.

bill

I would clean the carb first and try it. should make most of rated HP with that size . Tom

Tom, I am curious on how you came to that conclusion. I have been researching cfm requirements for that size engine which seems to be around 20 cfm but can't find any formula to calculate the cfm rating for a carburetor based on its venturi size. There is a lot of information on big carbs such as 650 cfm holleys etc but nothing on the small carbs for smaller engines. If your going on 1st hand experance, that's OK in my book anytime, but was just wondering if you had an engineering background and had any reference to cfm formulas for carbs. The little carbs are suppose to be somewhat linear and the formulas are not to complex so I might be able to understand some of that. Thanks, Bill

Bill: When I cleaned the carb. on my 4 cyl. kohler it was somewhat smaller than the manifold. On most engines cracking the throttel will give you high RPM without a load, If it is too small it would limit the rpm and power under full load. Mine runs at 1200 so it sounds slow at normal speeed. Good luck ,Tom

To answer my own question: I talked to Edwin Wright who is very familar with the 3A21 light plant and he said that the YB-2A carb was used on the 3A21 and was manf., by Tillotson. Evidently my uncle's light plant had a different carb installed at some time or they came with a couple of different carburetor selections. Ed agreed with Tom Jr., that the carb most likely needed a good cleaning and should support the rated hp (12 hp) of this machine. I found Ed's number somewhere in one of these posts but found that he has moved and has a new number (262-877-9175). He has parts for the YB-2A carb as well as mag, fuel pump, and engine parts for the 3A21 Kohler Light Plant (3KW). Many thanks to this forum. Bill