Small Engines (Lawn Mowers, etc.): B&S Fuel system, sediment bowl, thin cardboard

Question
B&S engine model 170402, Type 0714. Goes on my snowblower. For several years I could not get the motor running, then found out it was a dirty carburetor. Cleaned that out and it starts ok now, but if I hit a heavy patch of snow the engine slows down and almost stalls. If I press down on the handles so the front end goes up a bit, the engine speeds back up to normal. A couple times while using it today it stalled but started up ok.

I'm not sure I have everything adjusted right. I have the needle valve backed out 1 1/2 turns and the idle valve 1/2 turn out.

This engine has a glass sediment bowl directly under the fuel tank. Over the top of this is a fuel shut-off valve. While working on the carburetor I had this shut off. I opened it again, but how much should the valve screw be turned out? I have it about 1 turn. Is one turn enough. Should the valve be turned out as far as it will go? How much should that be opened.

If the fuel shut-off valve isn't opened enough, would that cause the slowdown or stalling problem? Should the needle valve or idle valve be tweeked a bit? If so, is one more likely than the other to cause the power loss or stalling?

One more question. The gasket on the fuel sediment bowl is worn. I don't have a replacemt right now. Is there anything that can be used as a temporary substitute? I covered a piece of thin cardboard with silcone caulking to make the cardboard a bit rubbery, but don't dare try it out, because I don't know if the gasoline will disolve the silicone and make a mess in the carburetor.

Thanks.

Answer
First off initial needle valve settings are 1 1/2 turns for the main jet, 1 turn for the low idle jet. These are just the rough settings to get the engine to run, and need further adjustments. When adjusting these valves the low idle is done at just that, a lowest idle possible, adjust till you have your best rpm, and a steady smooth idle. Then idle up to full idle, and adjust the main jet, done the same way till you have the steadiest idle, and smooth running. With some pieces of equipment you will need to turn the main jet a tiny bit to the rich side (screwing it out from the seat) a little more to compensate for the load it will be under when operating it in the snow. The low idle will remain as it is, it has nothing to do but provide a smooth low idle, and has no bearing on operation under a load. I have run into this same problem with tillers, and such too. What makes a good running machine at idle does not sometimes have the correct mixture it needs under a load. The sediment valve should be in the full open position, and should be set there before any such adjustments. Go to your local automotive parts store and buy some fuel resistant gasket material, and make your own bowl gasket from this, until you can acquire the correct gasket, maybe at a tractor supply store (they use those type sediment bowls on the late models).  Good luck, Tom