polaris 90 engine "missing" - dealer says no fix

We bought a Polaris 90 for our grandson last month - we have restricted the throttle by adjusting the throttle screw.  In hot weather it keeps stalling - in cooler weather it pops and misses.  We have had it back to the dealer twice - they advise they have contacted Polaris and there is nothing they can do to stop the miss - claim it is a "lean mixture problem" and the carburetor is preset at the factory and there is no adjustment on it.  We even dialled the throttle back up and it still does it (after we were told it was only a "lean mixture problem" at low throttle)  This is a gently used 2009 - they have also tried out their brand new 2009 in stock, and advise it does the same thing.  So they are saying "oh well" that's the way it is. Needless to say we are really frustrated and disappointed - has been in the shop more than at home - and they say there is no fix.  I can't believe Polaris can build these things with a "miss" and say - well that's the way they are...  Anybody else have this problem?  

Hello, my name is Ryan and I have been a Polaris Technician for the last six years. With the introduction of the new 4-stroke 90's back in 2007, we had a lot of issues with runability, mainly at idle. The dealer is correct about the machine being set up lean from the factory but there is an air/fuel mixture screw that takes a special D-shape screwdriver on the left hand side of the carb that can be used to richen up the fuel mixture at idle by turning it in clockwise. In the experience that I have had with these units, they are cold blooded and if there is a significant temperature change, the carburetor does need re-adjusted. An idle jet a size larger or using a jet drill to bore the existing pilot jet to a size larger works very well for better starting and idling. Polaris has to adhere to the EPA laws on all of their products and on carbureted units, they are set up way to lean to meet these EPA restrictions and Polaris cannot recommend changing anything for liability reasons. The dealers are even advised not to tamper with fuel mixture screws or they can be charged or fined. This is rediculous and I personally do whatever it takes to make the machine run right. I hope that this helped.