I have two 850's a 20 Khaos and 21 RMK and both are dirty running plug foulers. The 20 started life with a GGB can and had plenty of fouled plugs, usually on the PTO side after a cold start. It has the newest Polaris flash on it and I went back with the factory can it still fouls plugs. The 21 is all stock motor wise, including the can and I can almost guarantee a plug swap after each ride. They both run amazing when out riding, the issue is only on cold starts in the morning. I let the sleds completely warm up before touching the throttle but as soon as you do they instantly foul the PTO side plug. I've recently swapped the 21 to the EYA plugs and going to see how that works out. It's frustrating to change plugs every ride but at least it doesn't affect the overall rideability of the sleds when it counts. Both sleds are powerhouses and I don't feel like its a cylinder issue like some here believe.
Fouling spark plugs on cold start
- Thread starter HpPerformance
- Start date
Mine doesn't foul the plugs even moving it off the deck right away after starting. Saying that it hasn't seen much below 0 Celcius this winter.
Honestly buy a doo I’m on a 19 850 RMK it still floods out after the new flashes. My buddy’s 2021 850 flooded at 12 hrs so it should be past break in. I’m going doo next because you can’t even change the plugs on the trail because they just run. I get it I’m not happy about it and I have ridden Polaris since day one. If Polaris wants to keep making sleds that struggle to run just switch
I had a 2019 850 a 2020 and now a 2021. And never have had one plug foul or any other trouble with any of the three. Sounds like I have been extremely lucky. My 2019 never got the up dated flash either it ran awesome every bit as good as the other two. I Only put 300 miles on it though before I traded for the 2020. ?
Could be something completely different, but my 800 (2018) fouled 12 plugs on the left cylinder in the sled’s first 17 hours. Always during cold starts. Would idle a few seconds....then drop the left cylinder. To date it has never fouled a plug on the mag side cylinder. Otherwise it ripped and always started 2nd pull cold and 1st pull hot. Dealer kept trying to tell me it was normal and to wait for it to come out of break-in mode.
Finally I dropped the sled off with the dealer and they discovered the left reed block was pretty seriously warped. They said it looked like possibly a casting defect. They replaced it and no more fouled plugs now at 49 hours.
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klarkkentster
Well-known member
Nice. My dealer is still waiting on direction from Polaris.
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A possible fix to 850 Polaris plug fouling could be a set of plug wires that produce a larger spark. I have run these but not on an 850. I wanted the extra flamage for more performance so maybe more spark plug flame ? could help. No guarantees given or insinuated.
Nology wires.
Nology wires.
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klarkkentster
Well-known member
The plug boot is factory installed. The wire needs to be cut to length and installed on the coil thingy. The ground strap needs to go to a frame bolt. A two-three beer job. No biggie. I’ll go have a look and snap a pic for u.
I am putting a set on my Alpha.
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klarkkentster
Well-known member
How did you like them- notice a difference?
I hadn’t rode the sled for a season before I installed them so I had no back to back comparison.
It’s gonna sound weird but it felt like there was more spark!
I had to do that. When putting it away in the trailer, I unplug the pump and start it. Then I let it run for a few seconds til it dies. Plug the pump back in and you are ready for the next morning.
If it doesn't start on the second or third pull for a cold start, unplug the pump because at that point you are just flooding the dang thing. With the pump unplugged another couple pulls gets it to fire and clean out the crank case. Plug the pump back in and it will fire right up.
We have seen multiple 850's riding together and some seem to run richer than others. Some didn't even need the flash updates and were fine. This leads me to think that sensors may not all be equal, such as pipe temp sensors etc.
I think many Polaris hard parts don’t have the same tolerances………
Leak down test?
Compression?
Port chamfer’s………
Cylinder to exh Y pipe fit……..
Injector spray patterns and flow rates……
Leak down test?
Compression?
Port chamfer’s………
Cylinder to exh Y pipe fit……..
Injector spray patterns and flow rates……
Chinese parts, US parts, Canadian parts, Mexican parts...all made in Taiwan.
Hey guys !
Same issue here with my 2021 khaos.
13 hours on it now. I’ve fouled 13 plugs on the PTO side.
I’ve tired BPR9ES, BR9EYA and BR9IEX
I ONLY have fouling on cold start. Always PTO side and I’ve tired long warmups, going as soon as cold goes out and going as soon as I’ve stated the machine. All foul.
For me it’s a consistent scenario, and here it is;
I put brand new plugs in the sled and it runs amazing. When the sled is running it runs AMAZING. I run for about an hour, come home and park the sled inside. The next day I come out. Start it, and it fouls PTO plug.. EVERY TIME. I replace both plugs, start the sled and again flawless. It seems like during the hour of use the plug is loading up on carbon (I ride trail, hills, mix of everything, I’m not gentle on the sled by any means). So when the sled is warming up on the 1 hour set of used plugs, she fouls. This happens every single time !!
To me it seems like a map issue and she’s very rich on the PTO side, maybe Polaris is running is rich to protect it. Never blown a plug on the other side.
Sled is currently at the dealer, I’ve had the reflash update and it did nothing.
I am not accepting trial and error, I paid $20,000 Canadian for this sled and it should be expected to work. We shouldn’t have to be doing this and doing that, the sled should work, period. Never seen something so unreliable. It’s very disappointing.
I’ll keep you posted.
Same issue here with my 2021 khaos.
13 hours on it now. I’ve fouled 13 plugs on the PTO side.
I’ve tired BPR9ES, BR9EYA and BR9IEX
I ONLY have fouling on cold start. Always PTO side and I’ve tired long warmups, going as soon as cold goes out and going as soon as I’ve stated the machine. All foul.
For me it’s a consistent scenario, and here it is;
I put brand new plugs in the sled and it runs amazing. When the sled is running it runs AMAZING. I run for about an hour, come home and park the sled inside. The next day I come out. Start it, and it fouls PTO plug.. EVERY TIME. I replace both plugs, start the sled and again flawless. It seems like during the hour of use the plug is loading up on carbon (I ride trail, hills, mix of everything, I’m not gentle on the sled by any means). So when the sled is warming up on the 1 hour set of used plugs, she fouls. This happens every single time !!
To me it seems like a map issue and she’s very rich on the PTO side, maybe Polaris is running is rich to protect it. Never blown a plug on the other side.
Sled is currently at the dealer, I’ve had the reflash update and it did nothing.
I am not accepting trial and error, I paid $20,000 Canadian for this sled and it should be expected to work. We shouldn’t have to be doing this and doing that, the sled should work, period. Never seen something so unreliable. It’s very disappointing.
I’ll keep you posted.
