Denis

how does it start? if it starts easy your on the right track.once it starts you should within a couple of seconds have to reduce the choke some or it will kill.as you reduce the choke within 30 seconds or so of starting with no load it should stay running full throttle without the choke. if you need a longer choke period  to obtain the above the main needle is too lean. if the full throttle running with no choke is almost instantanious you are probably too rich. the initial on both needles is 1 1/2 turn out from lightly bottomed,however don't be alarmed if it's off as much as 3/4 to 1 full turn on the main.the idle mixture once fully warm can be adjusted as you have stated,somewhere in the middle of lean and rich stumble. the tell tail of getting close will be 1. when completely warm you can idle it down for 10 seconds or so and smartly advance it to full throttle and it doesn't stumble.if this is off too lean will just cause the motor to die completely,too rich and it will chug black smoke and cough and eventually go to full rpm. once you are close on the idle mixture and slow to full throttle without stumble the next test is under full load. i have found by slowly turning the bottom bowl screw out  1/8 turn at a time(richer) and trying it in a gear that puts the most load on the engine in heavy snow without stalling it out by overfilling it you will get the high speed mixture set for the most power.any leaner than this and you will get the symptoms you described in your post. if it cuts out under full load too lean will backfire through carb and too rich will cough black and choke out. these carbs are not mikunis and are not very sophisticated so they do not run perfect.the best you can hope for is 1. easy starting,2 no stumble going  from low speed to high speed ,and the engine pulls the load within reason at full throttle. if you can achieve these three settings you are in the ball park. i have found a little rich is better than too lean but if you get it too rich and it doesn't start with the first couple of pulls you can wet foul the plug and it will be difficult to start .  my slow speed mixture adjustment was very close to 1  1/2 but my high speed mixture was way lean at 1 1 /2 turns,it's more like 2 1/4 from bottom. let me know how you do. hope this helps. mkd

  this is how  the companies make there money....  im surprised no one on this forum has mentioned it in the past.  when you purchase a new machine " disassemble" and anti-seize stuff.  my small engine teacher here in minnesota worked for the polaris dealer and the upper people told him this exactly,  that this is how the make they money is selling parts later.    take briggs and stratton..... right now we are sellin g a 5hp vertical mower engine for $139.00.   2 yrs down the road from proper maintenance, i will sell him a new $40.00 carb plus gaskets and such.   get the point.