I recently started having some performance issues with my '11 850. When the engine is cold it will barely keep itself running. Sputters and runs about 700 rpms. Extremely rich. Sometimes have to work the throttle to keep it running. When I do that, it will die when I totally release the throttle. It is almost impossible to restart after that. It floods out and you have to let it sit a while before restarting. After it's warm, idle is fine, if maybe slightly rough. When trail running, it will power out if you put a load on it, such as climbing or getting into some snow. It's getting to where I almost need to stop and put it in low, where high should be no problem. Tried starting out in about 6" of snow last week. Had it in high and hit the throttle. It wouldn't spin the tires and slowly built rpm's and wheel speed.
Plugs are in good shape, air filter is clean and I can't find any loose or unplugged wires. No codes are being set. I adjusted the throttle cable to specs and that did not help. After that didn't work, I have tightened it up to increase my idle to aid in cold starting/warmup.
Any thoughts or suggestions? Trying to avoid a trip to the shop for obvious reasons, but this is unacceptable performance from a once incredible machine.

 

Anytime you have to tighten up the throttle cable on an efi machine (dangerous idea!) to keep it running,then it might be time to have this machine checked out on Polaris Digital Wrench.It could be as simple as reprogramming the computer(reflashing)the software will show any problem area and fix it! There's only so much a DIY type of person can do on these machines. Don't know about other shops,but we charged 1 hr labor and solved a lot of people's problems for a few bucks. A lot better than spending hours tinkering with it trying to guess what's causing the problem. Plus sounds like you could be having a clutch or belt problem by your description. OPT

 

Thanks for your reply OPT. It's frustrating when I can't diagnose and fix something. Kind of the way things are going with electronically controlled systems. They are great and there's nothing better when they are working correctly. However.......
I know what you are saying about using the adjustment to control the idle, but sometimes you just have to do what works. I can gain 200 rpm's just by turning the bars to full lock. But knowing and being aware of it relieves some of the hazard. Just have to make it through our big New Years Day ride and then I guess I will admit defeat and take it in.

 

OPT,
So here is what I found out. All eight valves were hitting the top of the pistons. Both pistons have 4 little half circle indentations in the tops from the valves hitting. The valves themselves show absolutely no damage and the rest of the engine still looks like brand new. What they don't know is why the valves were hitting. The warranty company is sending an adjuster to look at it before approving because it is an unusual case. Sun was impressed by the over all condition of the atv, which also plays in my favor. Fortunately I did have the break in service performed there at the dealer and have purchased all my oil change kits there, so there is a paper trail of sorts showing it has been regularly maintained. For those who say it doesn't matter what oil you use in your atv, let me just say the question was raised about that. I have used nothing but Polaris fluids just to cover my a$$ if something like this ever came up while under warranty. When all is said and done I will have new pistons, rings, bearings and a rebuilt head. Basically a new engine.
Another mystery is the low compression. The engine was within tolerance when they performed a leak down test on each cylinder. The valve problem would not let it build as much compression as it was supposed to, but would seat well enough to hold what it did build.
If it was a timing issue, wouldn't it be the exhaust or the intake valves, and not both?

 

Freaky damage. Like you said if it was a mechanical timing issue then it would usually be the intake or exhaust valves taking the brunt and engine would stop before the other valves were damaged. All 8?? Only thing I could think of is either connecting rod bearing failure(BOTH rod bearings would have to go out at the same time??) or cam sprockets/chain,a batch of soft treated valve springs,sheared cam dowel pin?? Glad you have a paper trail and an adjuster is coming out to look it over. Had the same sort of thing happen to my wife's 89 Chevy Corsica with only 22,000 miles years ago. They had to replace the valves and camshaft under warranty. Keep us updated as to the exact cause. OPT

 

If they determine the exact cause I will let you know. All the bearings look to be fine and no sign of any physical damage to anything other than the piston tops. My fear is they will just do the rebuild and I will never know what happened. I have searched and can find nothing about this happening to anyone else's 850. (or any other engine) I seem to have a special, one off model. It has run like this for a few months without engine failure. It was still running when I dropped it off.

 

Here is a wrap up on this thread.
Turns out the tensioner for the timing chain was broken, so there was slop in the chain. It didn't jump a tooth, but the timing was all over the board. They did a total rebuild of the engine and my extended warranty paid every penny of it. Now I'm back in the break in process again and soon to be back up to speed.

 

Times like this is when an extended warranty is worth the cost. I've rebuild several engines,transmissions in the past that had extended warranties and most of the people had the $50-$75 deductible plan that was offered through GE. Not a bad out of pocket price considering what all I had to do and what it would have cost without the warranty.Good luck on the machine. OPT