Stainless steel needle on a brass seat will wear less quickly than the others you mentioned. Either needle tip works fine. You may want to install a small inline fuel filter to help keep crud from flowing through and keeping the needle from seating properly. Even though Lawn Boy claims to use "tank filters" or even inline screen filters like found on the metal Walbro carbs, I've had small pieces filter through to hold the needle open enough to drain the tank out overnight by flooding through the carb and out the airbox. Some recommend fuel valve shutoffs, but I've had good luck by installing filters after carb overhauls.

I would check to make sure you do not have a shear pin broke.Could be one of the cross augers has one sheared?Could also be that they apear to be turning while not under load in snow.But when it gets in snow it stops? What could have caused it is it froze when you put it away.Then when you engaged it thats when it could have snaped? Also it could have a chunk of ice lodged in the discharge you can not see? Could also be your belt needs tightening or it got water soaked if snow melted and ran down into the belt pulley cover? I have a Simplicity 1180E 11HP 32'' I tightened my belt just a little.Did not show any sighns of needing it.But I noticed the engadgement level worked slightly easier then originally.Not sure about your model.But its a quick easy tweak just a few turns on the linkage turnbuckle. I do not have a heated area.If it gets above freezing and snow melts a little on the snowblower then freezes.This can cause a problem.I blow mine off as best I can when done.Or if the sun comes out enouph to melt it off.I let it melt and then blow the water away best I can.When it goes below freezing and I need to use it.I check to make sure the impeller and cross augers turn slightly before starting.Just to make sure its not froze up.Water could freeze in the impeller housing very easily.

As it happens, although I am a regular reader of this board I found this posting because I was having exactly the same trouble with my 16hp Vanguard. I was out cutting an area of my property that only gets cut once a year, so it was pretty heavy and slow mowing. I noticed that the tractor was bogging down and starting to blow black smoke while it was under load, it also was running roughly at idle and seemed to be missing on one cylinder. I quickly brought the tractor in and turned the motor off. It was so quick and there was so much smoke I thought I had damaged the rings or the valves on the engine. As a previous poster had mentioned I tried running the engine with and without the air filter. As soon as I took the filter off the engine stopped smoking and ran smoothly. This is probably the cause of some fuel delivery problems I was having earlier this summer as well. The interesting thing to me is that this is a new filter, installed in June and is one of the genuine Briggs "Black" gasket filters. I will buy a new filter from a different source this week and hope it clears up the problem.

You do not need to "split the case". In the parts list, item # 113 is the vent. Remove that vent and invert the transaxle assemble over a suitable catch container. Let it drain upside down for a day or 2 (good winter project). By the way, the illustrated parts list might make it seem as if the vent is located on the bottom of the case. It is on the top when the trans is in the tractor. Hydro gear just turned the image on its side. And it is not "oil lost" (as in volume) that causes the problems. It is that the oil in there has become so degraded and contaminated that it hardly resembles what it was when new (regarding its hydraulic capabilities).