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850 still Bogging and fouling Plugs after Break in

Motorbreath_ said:
I hear sometimes about guys Polaris' actually being reliable, but its few and far between.. When you've experienced the heart ache yourself it really takes a toll on your confidence for a certain brand.

Nothing feels better to ride (especially for my style of riding) than a pro rmk. I just can't do it to myself again though.. and my wife constantly reminds me of the issues I've had with previous Polaris snowmobiles.. lol.

Hopefully someday I can get on another one..
Click to expand...

I’m with ya. I’m really hoping my sled with the updated engine and fuel injectors has some reasonable level of reliability. Riding for me is more then a hobby - definitely positively impacts my mental health. I’d be happy with changing plugs every 6-8 rides. But not every ride. My old 99 RMK700. Never changed the plugs once and it was carbureted.


Sent from my iPhone using Tapatalk
 
First trip out this year and one of the 2019 850 started bogging and fouling, ended up being a broken power valve cable.
Ran good after that ...
All our 850’s currently running good, however all have their quirks. Some have popping, periodic little bog, and some starting issues. I think Poo just haven’t got them dialed in yet.
My 2020 is only one with 21 flash.
One 2019 has Outlaw twins with head and flash....We have various clutching, 2-stock/1-SLP/2-TRS.
 
2021 khaos 850 155 qd1
Polaris VES extreme
91 noneth
600 miles

Fouled plugs almost every cold start and after a long break. No luck with bpr9eix
I found plug boots migrating, terminal nuts screwing off, lots of black dust in boots.
Ended up disconnecting my key. Swapped boots to the Lb05ema. Dielectric grease on wire and in cap. Ngk 7788 plugs.
No longer foul plugs, easier starting, picked up ~200rpm
 
Jumper out throttle safety switch, $40 from tki, make sure tether connection is good.

Or switch to magnetic tether. Just went through this with my turbo 19 850. TSS switch was acting up from day one.
 
SlugExchange said:
2021 khaos 850 155 qd1
Polaris VES extreme
91 noneth
600 miles

Fouled plugs almost every cold start and after a long break. No luck with bpr9eix
I found plug boots migrating, terminal nuts screwing off, lots of black dust in boots.
Ended up disconnecting my key. Swapped boots to the Lb05ema. Dielectric grease on wire and in cap. Ngk 7788 plugs.
No longer foul plugs, easier starting, picked up ~200rpm
Click to expand...
There was a thread over on Harcdoresledder about this. A guy was constantly fouling plugs so he disconnected his keyswitch and he had no more issues after that. I believe he ended up cleaning out the plugs and putting dielectric grease in it for a permanent fix.
 
If fouling in your 840 continues use these..

Polaris VES (gold) oil
NGK 93427 BPR8ES-6 (solid top)
NGK TB05EMA 8636 Spark Plug Cap Resistor Cover Boot
Shell Premium non-ethanol gasoline

Check your oil injection rate.. heavy oiling rate from ecu mapping is fouling the plugs. (heavy rate = 26/27:1 total and will work with above).

If detonation light illuminates after switching the above parts. (cold days) Set dash fuel selector to ethanol mode.

The above is a solid work around.

Do not use screw top spark plugs ever! I have fixed 7 machines this season (4 skis) with odd running issues that were directly related to arcing plug caps and screw tops. GET RID OF THEM! Once the screw top starts arcing it also damages the plug cap. So you have to change both!

The "8" plug is one step hotter than the "9".

Also note the BPR9ES spark plug has a 10k ohm resistor vs 5k ohm on "8". This further weakens the spark especially considering the 5k ohm plug cap.

The "-6" is the preset gap of .024". The preset gap has been working fine and you can go up to .028" no problem.
 
Last edited:
How to check oil usage

Use oil mix cup to fill oil tank to top. Use a consistent point to measure usage from. Fill to same spot each time you fill up. Measure oil fill volume in ounces.

Fill gas tank to the top and record gallons. use consistent fill point.

calculate and trend :

Fill-up #1
46 ounces of oil in the tank
9.5 gallons of gas

9.5 x 128 = 1216 ounces
1216 / 46 = 26.43

Rounded mix ratio
26 : 1
 
greasemonkey3406 said:
There was a thread over on Harcdoresledder about this. A guy was constantly fouling plugs so he disconnected his keyswitch and he had no more issues after that. I believe he ended up cleaning out the plugs and putting dielectric grease in it for a permanent fix.
Click to expand...
Sorry for my ignorance on this one, but when you say unplug the "keyswitch", do you mean simply just unplugging the switch where the key goes in right on the console? Cheers.
 
stevo313 said:
Do you know how or what the reasoning is as to why this helps solve the fouling plug issues?
Click to expand...
Speculate it's causing voltage leak after moisture gets in to the switch. Weaker spark will cause fouling.
Not sure if that's what fixed my problems as I did a few things at the same time but it's quick and easy to try. And now I can't forget my key
 
Step 1: Make sure caps and wires are good.

Step 2: Make sure tether does not have moisture in connection Or..... Replace with Durapro magnetic tether and don’t worry about moisture

Step 3: Buy $40 TKI throttle safety switch delete jumper and install.

Results: Sled starts and idles better even when cold. Sounds stronger and more throaty at idle.
No more fouled plugs or bog.

TSS switches are not sealed very good at all and react poorly to moisture / prolonged deep snow conditions. They have been Cat and Polaris’s cheap alternative to providing a factory tether for many years.

Standard tethers & tether caps also have a life span and don’t deal with moisture well or being pulled repeatedly. If you have pulled your tether multiple times even the cap will wear and cause problems.

Make sure your electrical is solid before looking at anything else. Moisture & poor quality switch / tether related electrical issues are usually intermittent and if you’re having theses issues you will beat your head against the wall trying to figure out what’s wrong. A simple tether upgrade and TSS delete switch will likely remedy the issues.

I’m no mechanic though so what do I know.
My 19 high boost boondocker runs like a champ now since doing those simple fixes. Wish I woulda known about this stuff first two years I had the sled because the problem was always there intermittently, it just became a whole lot worse as time went on. Last ride before I did the fixes I cooked 5 sets of plugs in 3 hours.

PTO side plug always oil / fuel soaked and mag side white when the sled would foul.
 
SlugExchange said:
2021 khaos 850 155 qd1
Polaris VES extreme
91 noneth
600 miles

Fouled plugs almost every cold start and after a long break. No luck with bpr9eix
I found plug boots migrating, terminal nuts screwing off, lots of black dust in boots.
Ended up disconnecting my key. Swapped boots to the Lb05ema. Dielectric grease on wire and in cap. Ngk 7788 plugs.
No longer foul plugs, easier starting, picked up ~200rpm
Click to expand...
Thank you - the stock spark plug boots are a huge pain to get on for sure. Did they simply unscrew from the igintiion cables? I also found this on another thread I thought was interesting. Anyone try this with the ignition switch?

www.hardcoresledder.com

BOTH 2020's are fouling plugs while warming up

www.hardcoresledder.com www.hardcoresledder.com
 
Tha
Mentzel said:
If fouling in your 840 continues use these..

Polaris VES (gold) oil
NGK 93427 BPR8ES-6 (solid top)
NGK TB05EMA 8636 Spark Plug Cap Resistor Cover Boot
Shell Premium non-ethanol gasoline

Check your oil injection rate.. heavy oiling rate from ecu mapping is fouling the plugs. (heavy rate = 26/27:1 total and will work with above).

If detonation light illuminates after switching the above parts. (cold days) Set dash fuel selector to ethanol mode.

The above is a solid work around.

Do not use screw top spark plugs ever! I have fixed 7 machines this season (4 skis) with odd running issues that were directly related to arcing plug caps and screw tops. GET RID OF THEM! Once the screw top starts arcing it also damages the plug cap. So you have to change both!

The "8" plug is one step hotter than the "9".

Also note the BPR9ES spark plug has a 10k ohm resistor vs 5k ohm on "8". This further weakens the spark especially considering the 5k ohm plug cap.

The "-6" is the preset gap of .024". The preset gap has been working fine and you can go up to .028" no problem.
Click to expand...
Thank you - do the stocks cap simply unscrew off the ignition cables?
 
Don’t you sell these?
If so, the way you posted is a complete bick move.
 
Last edited:
Not sure what I said that was a "bick move"? I was surprised they are selling for $40. I sell them for $20. I guess if selling them at a reasonable price to my fellow Snowesters' qualifies for that then I am guilty.

My apologies to anyone that read my post and was offended. That was not my intent.
 
Last edited:
It's a power valve calibration issue take it back to the dealer to recalibrate the power-valve PTO side will be wide open my 2021 was doing the same thing ran great the rest of the year
 
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