I was in Jackson Hole last weekend at a local dealer and was told the reason for all of the 800 problems were due the cooling system being maybe too good. He said after a ride at operating temps, when a rider stops and shuts the sled off the engine coolant heats up to 140-170 degrees, while the coolant in the cooler in the tunnel rapidly cools to around 100 or lower. Then when you start back up and run, the extra cold coolant rushes in and causes catastrophic damage to the "hot" engine. Kinda like putting cold water in an overheating car with the engine off. Multiple start/ stops takes its toll on all of the aluminum parts and starts changing shapes and sizes of pistons and cylinders and causes all of the scoring and finally seizing and breaking of pistons and skirts. Sounds reasonable to me. What do you guys think? Btw Mine went down so I have had this happen, not just starting another Polaris bashing thread. I love mine and as long as they pay for the fix and do it quick I'm good. The dealer said Polaris has a sled he is testing with some sort of a coolant bypass to remedy the problem. He said so far so good.
The reason for all the 08-09 800 burn-downs??
- Thread starter crf118r
- Start date
B
I kind of doubt it...there is a thermostat in the cooling system to control the water.
Don't believe it for a second.
J
in theory that makes sense i guess but it doesnt account for all the issues. in my sled you could see waves in the piston skirts... and a severe excess amounts of play w/ the pistons sitting inside the cylinders. to me it looks like a bad batch of pistons. the other four i have seen at work all had waves in the pistons as well and excessive amounts of slop. single ringed pistons could be an issue all on their own. luckily i cought mine and was able to pull the pistons before they damamged the cylinders since the mono cylinder is on back order for who knows how long. but you can see when you tare them down that the pistons get to much play over time and with the extra clearance it allows them to slap the exhaust ports in the cylinder walls w/ the piston skirts on every rotation which in time chips away at the cylinder putting chunks of aluminum into the cylinder, cracking the cylinder walls around the exhaust ports and burning down the motor. just my .02 cents
G
I dont believe that for a second either. My 600 ho carb had the same cooling system and would do the same thing. You shut it off, it would read 124 F and when you start it back up agin it would read 150 F and then rapidly cool down to 112 F. You dont hear of many problems of blown motors with those engines.
H
I heard it is a electrical issue causing a intermittant lean run and scorching pistons. I heard this from a fairly reliable source. BTW, for all those that have a hole burned into top of piston from say "modifications" I have also heard Poo is calling for review and all parts. So be prepared you may NOT get warranty to cover your problem.
S
heard them all but the two that keep coming up are:
lean spot 6000 - 6500RPMs. different mapping was installed. same problem.... cant be that
clearance with the pistons and cylinders walls. ding ding
lean spot 6000 - 6500RPMs. different mapping was installed. same problem.... cant be that
clearance with the pistons and cylinders walls. ding ding
S
btw my friend got a new crate motor from polaris. i didnt ask if there was anything different with this motor but it seems to run fine so far 
its not a lean spot its a hot spot where they cannot control the amount of heat on the decel side from 5-6k...they tried to fatten it up to cool down the piston and that extra fuel hurt more than helped by igniting in the pipe and scorching the piston causing a seize
Don't the 6 and 700's have heat exchangers in the fronts that the Dragons 800's don't have? The dude said something to that effect when I talked to him. That would also explain the poeple with 800 RMK's that aren't having the issues. Not sure just trying to compile info here to get a handle on what's up. Buckshot, don't you think the thermostat would let cold water rush in as it would be hot enough sitting to open the valve before starting back up? And wouldn't heat warp a piston if this happened frequently? Not sure. I have heard the lean or hot spot hypothesis but it would seem they could remedy this with the new mapping and fuel rails they are passing out on rebuilds or swap injectors for some that work differently. Of course I don't know my source from Adam but this sounds like a reasonable take on what is happening here. I would be happy to not have another break-down.
I don't believe it's the cooling system. My 08 D8 runs at only 120 degrees whether I'm on hard pack or pushing powder. I even brought this low temp up on this web site last year. The on-off cycling counts would have to be excessive to accumulate any metal fatigue. After all the info bounced around, I firmly believe it has to do with fuel mapping and piston/cylinder clearance.
D
BINGO! Well stated.
Any rebuild make sure they check the distance between the cylinder and the piston. Mine was beyond spec. Too much slop is not a good thing.
I'm not disagreeing with you but the heat is not generated while the engine is running, it's after shut down when the coolant stops circulating. Upon restart all of the cold coolant from the huge tunnel cooler rushes in and starts warping things. This is how I understood it at least. The engine will reach much higher temps than normal operating temps just after shut-down. Seems like things would expanded some from heat and then super cooled after re-start and shrink back down quickly and squeeze and score the piston. Again, I'm only relaying what I heard as I have no clue what to think, only my own assumptions.
S
Guys, its an E.C.U problem, the E.C.U. has a meltdown, then the regulator tries to correct the problem and cooks itself in the process, then this screws up the the C.F.I.(fuel air mixture) and what happens? It goes lean thus causing the the piston to seize and all other problems, the cure well the only thing I can come up with is to find a different brand of E.C.U. this could be tough, I have heard putting a battery in will fix the problem, but this dose not stand to reason because the E.C.U will still fry, any suggestion???
when my ecu went down it did not cause my engine to fail....the regulator went out took out the ecu and my sled stopped. I have 300 miles on the new ecu with zero issues.
Also it is not a cooling system related blow up.
Also it is not a cooling system related blow up.
If everyone here is so sure what the real problem is then why the fluck doesn't Polaris have this trick fixed? Seems a bit fishy to me. Fuel injection has been around for a long time. We have all had enough of this BS. There can't be that many stupid people in R$D can there?
Because a fix cost money. In this case, lots of money. They are trying everything they can to fix this w/o spending big money and putting the dealers in repair mode (more than they already are).
Ski-Doo did a fix last year for the XP's. They keep losing belts, so they opted for a $20 gear and geared the sleds down. Cheaper than a belt or other fix.
the fix is coming
Then why is my '08 600 hasn't had any issues the way you are describing it? And it has 5600+ on it. Blew one piston but that was it. Lol, some dealers/guys can make up anything they want to and the naive will believe it. CFI's need a proper calibration and the electrical needs to be worked out.
I have read this and well, the water in the tunnel isn't super cooled by a long stretch. Feel you tunnel when you stop it is very warm. The temperature in the cylinder will rise and then it will fall also shortly after. The fraction of a second after any water that is cooler than thermostat set temp hits the thermostat it closed and now you no longer have a big gush of warm water circulating around the cylinder. I don’t think the theory holds any water but this whole thread is just postulating anyway. Electrical failures have likely resulted in some of the failure but not all. The tell tale signs of a lean condition are present on both of my top end burn downs and no indication of an electrical issue has presented itself.
Now having dealt with after market fuel injection in my jeeps I can say that trying to crate a fuel map that works in all conditions is very difficult and that is why in most cars systems let a single sensor handle the majority about 70 to 80 percent of the fuel flow requirement (the O2 sensor). The other sensor only provide trimming for this 80 percent. Then if the MAP or Throttle position get out side of a certain range you run on a fuel curve map much like our sleds. There are variation on how this out side fuel map is handle but usually Manifold Absolute pressure or Mass Air Flow are used along with RPM.
Polaris as I understand based there map on RPM, and Throttle position for the main parameters with trimming from the pipe temp. To be able to map all possible riding condition and throttle positions and engine loads with these parameter seem very difficult to me, and I wonder if this isn't part of the issue. Just my two cents
Now having dealt with after market fuel injection in my jeeps I can say that trying to crate a fuel map that works in all conditions is very difficult and that is why in most cars systems let a single sensor handle the majority about 70 to 80 percent of the fuel flow requirement (the O2 sensor). The other sensor only provide trimming for this 80 percent. Then if the MAP or Throttle position get out side of a certain range you run on a fuel curve map much like our sleds. There are variation on how this out side fuel map is handle but usually Manifold Absolute pressure or Mass Air Flow are used along with RPM.
Polaris as I understand based there map on RPM, and Throttle position for the main parameters with trimming from the pipe temp. To be able to map all possible riding condition and throttle positions and engine loads with these parameter seem very difficult to me, and I wonder if this isn't part of the issue. Just my two cents
