Help with carb problem please!

Boy, am I stumped. I have a carb problem I can"t figure out. I have a Homelite T-10 with a 10hp Briggs engine. I have put a kit in the carb, and I know the thing is old and pretty loose, but at one time I had it running fairly well. Now I have a flooding problem. When I turn on the gas and start it up, after about 30 seconds it starts to run badly, and I see the carb body start filling with gas....float stuck open. That I know. The float chamber is completely full of gas and it is filling the body from the overflow...I assume. So I have taken the thing apart about thirty times now..seriously....checked the float...not leaking...replaced the needle several times, and test by blowing into the fill tube. It passes air when upright, and does not when upside down (float needle closed). I put it back on the engine....and it floods every time. I have no loose dirt or debris in the carb, gaskets fit tight. I have played with several float levels, including the spec setting, and set low so it would stop flow when the float is barely moved. It floods every time. Now, in blowing cleaner through all the various orifaces, I see that there is a vent at the top of the bowl that emptys into the body below the air filter. Is there some kind of siphon action going on? Any help is appreciated!

If it has a valve seat that screws into the body it could have a leaky gasket or loose seat. You need a carb. pressure tester to normaly find a small leak, Just using your lung pressure is not enough, you need about 3-5 psi of steady pressure.Hope that this helps
Ed

Thanks! Didn't think of the pressure...it has a pressed in seat. I can press it out some by inserting a screwdriver into the inlet and forcing it out. Can I replace just the seat?

Float, needle, seat. Only three things that would make it leak like that. Float, if brass can develop a crack so fine that you can hardly see it. I've run into 2 like that. Dried them off and tipped them around until a wet spot showed up from the little bit gas in them. Vacuumed the gas out by blowing compressed air past the crack and then soldered them up.
Needle and seat is obvious...they'll just need replacing...don't know about a pressure fit seat.
You could bend the float tab to exert more pressure on the needle.

Thank you. When I take the float out, it is very light, but all the gas may have leaked out already, so I'll check that. I'll see if my local mower shop has just a seat that will fit.

WOW! I found a hairline crack in my float! Thank you for the hint!!

Best to replace the float if you found a crack. I was pressed so I just dried them out and touched some solder to them. They're still ok. Seems that age does something a very fine crack will somehow happen. Doesn't take much gas to make it sink.

I have had floats with about 2 drops of gas in them. Really hard to tell there is gas in them even when shaking them. But it makes them heavy and run like krap.