I think the problem in this thread related more to the 550 Fans in Edge Chassis, made after around 2003. Not sure if the same problems existing in the earlier RMK version. Anyway, after reading through this thread, I still went ahead and purchased 2 - 2004 550 Fan Sport Touring. Both of these had top ends rebuilt over the last two years, and have close to 3500 miles each. They did not have any of the modifications mentioned above (not even the oil bleeder kit), and still must have been running fine to have that many miles.
Since the problems were also associated with the type of trail riding in the 30-50 MPH range, I did not put too much trust in the miles, and installed the hood duct kit. The kit from Polaris comes with Oil Bleed Kit, Fuel Pump Relocation Kit, exhaust Y pipe insulation, and additional cutouts into the nose cone front and sides for better air circulation. The Kit was around $180 and took me a couple of hours to install. The kit fit perfectly over the fan and aligned with a new air intake that I had to cut out in the hood. Now the outside air (30-40 degree even on hot days) is sucked directly into the fan, that was previously sucking hot air from inside the engine/exhaust compartment(175 degree). The kit said that it is for 2007-2009 550 fans, but fit perfectly on the 2004 fan.
Did'nt just stop there. Got me some exhaust insulation (Heatshield) and covered most of the exhaust pipe. Cost of that was about $100 plus 30 minutes of my time.
I picked up the sleds cheap for $1250 each. Put in another $300, and I think I am all set. I may still change the needle jets (another $50 plus labor), but am not sure if the needles were changed per Polaris recommendations when the top ends were re-built (Any idea on how to check if these were upgraded?).
These are just my play sleds for when I want to go 2-Up, as my family typically rides individually on RMKs and a AC King Cat (in the west). That can tell you that I an not a die-hard brand fan of Polaris or AC.
Folks on this forum and others similar forums have spent a lot of time and effort on explaining some basic problem (heat related) and offered a combination of solutions. Increasing fuel richment (changing needle jets and settings), increasing piston clearance (so expansion due to heat would not sieze the engine), oil bleed kits (so that hot oil does not form an air bubble), fan duct kits (to get cooler air into the engine), fuel pump relocation, and additional openings in the hood and nose pan all attempt to reduce engine temps. The 550 is a big motor for fan to cool. In 2003-04 polaris attempted to get a little more umph out of the motor and may have leaned it a bit too much. Combined with not so effecient (cooling) Edge chassis design, and they had a disaster. The 550 fan engines were manufactured (with most of the above mentioned upgrades) all the way into 2009 (Not sure about 2010 and beyond). So there does not seem to be a mechanical issue with the fan motor after the corrections.
With the understanding that the money I spent on these two sleds was "play money", I have no problem if it all goes south. As in Las Vegas we say, gamble with only what you can afford to lose. I dont intend to use these to go too far or back/forth to work and always have my Sat phone, GPS, Snowshoes, and Survival gear with me. So safety risk is minimal.
In reading these forums, we should understand that most folks who turn to these are the ones who have problems (as most feedback is negative). No one whose 550 fans are running great will Google "Burndown problems and Jetting Issues". Out of tens of thousands of 550 fans sold, there may be problems with a bunch of those. Others are running just fine.
Thanks again for everyone on this forum on making us educated on the issues related to the 550 fan. Now lets go out and have some snow fun....
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