What does the slack in the throttle affect? I have about a 1/16 but can open it up a bit I guess. Update: I opened it up a bit and it had no affect on my problem. I'll say it again it feels like it just runs out of gas when you have the throttle pegged it pulls strong for a few seconds then starts to fall on its face and unless you back off it just dies out, just like you have run out of gas, then when you back off it acts like you flip the switch to the reserve tank and all is good. I'm wondering if my fuel pump is weak even though it holds vaccum?

 

Sounds like we have a identical problem I'm dealing with at this very moment.It started a few months ago,it only starts sputtering and popping going up a steep hill but mine will not make it,roll back down and back up over and over and cannot make it over.We tried replacing the needle and seat with no help as well as adjusting the float.We bought a new carb $375 and bolted it up yesterday and tried a hill with the same issue,I do not think it is starving but running too rich due to the black smoke from the exhaust and the overflow is dripping.I'm thinking float but not sure.I looked in my tank and noticed some water seeing it's heavier than fuel it make be sucking water??

 

The water is definately an issue, on mine it wasn't running rich but lean and running out of fuel when going uphill. Mine is running good now after I raised the needle (lowering the clip one notch so it's on the fourth instead of the middle or third notch which is stock.) Raising the needle allows more fuel to enter the carb at a lower throttle opening. I tried the needle at different positions and could exagerate the problem by lowering the needle which led me to narrowing down the problem. You might check to see where your's is at just by chance. I got pretty good at changing it by not taking off the carb. After taking off the airbox and carb support bracked you can just loosen the carb boot hose clamps, spin the carb and take off the top plate to get to the needle. At a different point in time I did have a float problem when I would point the machine downhill, mainly when plowing snow, it would sputter and die and I noticed fuel leaking from the overflow. I fixed that by adjusting the float and all has been good since. As for the overflow dripping fuel I notice my doing that every now and then when I have the machine at an angle and just attribute that to how the overflow is designed. It sounds like you've got everything right with the carb, especially with buying a new one, looks like you'll have to look elsewhere. Good luck.