I just had a similiar problem. I used a small wire to check all holes and even soaked it overnight in gasoline. But, I think my problem was the screw which holds the bowl on was clogged. It has a center hole in the end of the screw and 2 holes on the side of the screw which were plugged, and therefore the carb was not getting gas. May not be your problem, but might be worth a look.

The bolt is clean. It's one of the passages directly above the bolt that is clogged.

The fuel inlet is wide open, and the bowl vent passage and primer passage from the welch plug to the air filter mount are both clear.

Anybody have a labeled pic or diagram of this carb? I can find plenty on the older style B&S carbs, but not the quantum.

If you can't blow air through the hole, then I would try just soaking it for 24 hours in gas. Then try the wire and/or air again.

With the idel screw removed, you must be able to pass carb cleaner through this screw opening, and it must come out that little tube. This circuit is the main running circuit. When ever you can't adjust this screw, it means that this circuit is plugged. Tag wire usually will clean it out.

I'll try to get a picture up tomorrow- this carb doesn't have adjustment screws (don't remember any Quantums having them, actually). I'm fairly certain that the brass tube leading to the venturi is the main running circuit. The passage I'm asking about is right next to the brass tube. (Brass tube is clear as daylight, btw- so is the orifice in the bowl screw).

Don't think that is a passage... Only the older Quantums had the side IC screw. When you are covering your bases, be sure that the intake seal is in place and the intake is secure and hasn't come apart. You would need to pull the shroud to inspect. To try and go further, you will need to soak the carb in a real cleaner or just replace the carbs~ $35

I hadn't thought to check the intake- Will do this weekend.

You may be right, it could be a dead passage. I've never worried about it in the past because the blockage was always somewhere else. This current carb is absolutely clean every other place, so I assumed this hole must be the blocked one. An intake problem is starting to make more sense.....

Thanks Tom! I'll let you know how it goes.

These carbs seem to be most troublesome.Go figure?OK,i recomend using a plastic gas can to alleviate any water or dirt being poured into the gas tank.You (or i always)take the pour spout off and look to see if any water has accumulated in the bottom of can from condensation before pouring any gas into any mower/engine.Also look to make sure no dirt has found its way into the can.Gas tank empty - nows a good time to pull the tank,fuel line and carb bowl off the mower/engine and dump out any gas or water thats left.Use air to really blow the crap outa the tank and line.Let tank and line air dry in the sun (recomended for gas cans too)for a day or so if possible upside down so any missed gas or water will evaporate.Now check the fuel filter for clogs.Take the darn thing off and hold it to the sun light-you should be able to see right tru the thing or simply replace it.Now check the fuel line is it cracked?If so go to most any hardware store or auto parts store with fuel line in tow and show it to the sales person and say i need this hose.Hopefully the sales person isn't a complete idiot (i know some are) and will cut you the right diameter hose to lenght.You can use a carpet cutter or pair of side wire cutters to cut the hose to install the filter or ask the sales person to do so.Put everthing back together.You might want to replace the rubber gasket that goes between the carb and bowl - again while your at the store you can pick that up too but you'll probably need the engine model and type number along with,is it a Briggs engine or Tecumseh or what ever info (believe it or not when i've asked people what type engine they have.They get this dumb look on their face and say i don't know).Don't forget the paper gasket that goes on the bottom of bowl where the bolt that holds carb bowl on goes.You can purchase these two gaskets separetely or they come in the carb kit.If youre gonna take the carb off and clean it go for the kit.Also gasoline works well for cleaning carbs but i've found that specially designed carb cleaner works better.You can buy a gallon can in most any auto parts store reasonably.Basically you pop the lid off the can and drop the carb (taken apart) into the cleaner.Hint,tie a piece of wire to the carb to fish it out with later!Hint,got those jugs of used motor oil sitting around?Pour any old gas into the jugs you want to get rid of and make sure to put the lid on tightly and lug'em along with you to the parts store.By law they are required to take used motor oil (doesn't matter about the gas being in there too.)Hint,they also take in automotive anti-freeze.Hint,if you know someone who has a shop chances are they have a waste oil furance and will take your old oil/gas mixture.Just remember while oil isn't as combustable as gas.When you mix the two,they are very combustable!Its proably a good idea if you can to place your jugs of combustables in a sealed plastic container with a lid on it if your lugging them in your car (no plastic container-use a heavy cardboard box with lots of newspapers in the bottom to catch any spills).If you have a pickup truck,place in the bed of your truck and secure very good.Spilled oil makes one heck of a mess.Hope i've helped someone make caring for their gas engine more pleasent and saved you some money and headache.Peace,Gary

Oh boy...