I had a few backfires the last time riding. My quad has 72 miles on it. Well, I went to move it and it won't fire. I pulled the plugs and they appear to be pretty wet (fouled). I cleaned em' up with gas and put them back in and turned it over - I got a chug like it was gonna start and now she just rolls over again. I ordered some new plugs - I went with some NGK Irridium plugs recommended by another 850XP owner.

Is there anything else I should check? Not to happy with this problem. I did change my oil at 50 miles and didn't have the right tool to remove the filter - so, the oil level is at the top of the allowed maximum. Thinking this cold be another cause. Thanks in advance...Jeff

BTW - The plugs are a NGK-ILZKAR7A10(6043)

The are made for a 2008 Mercedes Benz 6.3 Liter - it is a compatable plug upgrade if you want to go NGK Irridium. You gap them a little wider and get a smoother idle - along with a much longer life.

 

Did you check for spark ? you could of sheered off your flywheel key when you had the backfires .

 

Likely the plugs are the issue,once they become completely fouled there isn't much hope of fixing them,and using gas on them only makes the fouling worse.

The NGK iridiums work great for me,ok me a of bit of research to come up with that replacement. I basically had to match them using measurements and thread specs.
They aren't quite as hot as the newer heat range 8 chmpion plug,but I had no issues with fouling with the NGK or the heat range 6 champions for that matter.
Make sure you let the machine warm up everytime you start it...in other words if you aren't going to run it long enough to warm up then don't even start it....that is what causes the 850s to foul plugs in 99.99% of cases.



I don't suggest gapping them though...the NGK iridums come pre-gapped,that part number is a .040 gap IIRC,which is plenty just verify the gap and run them.
I've experimented with wider than .040 and it isn't worth the trouble,it may net a little performance but idle will actually suffer with a wider gap. You can gap iridium plugs but you mnake sure you don't touch the electrode with any sort of tool...

 

[QUOTE=deerwagon;2871162]I had a few backfires the last time riding. My quad has 72 miles on it. Well, I went to move it and it won't fire. I pulled the plugs and they appear to be pretty wet (fouled). I cleaned em' up with gas and put them back in and turned it over - I got a chug like it was gonna start and now she just rolls over again. I ordered some new plugs - I went with some NGK Irridium plugs recommended by another 850XP owner.

Is there anything else I should check? Not to happy with this problem. I did change my oil at 50 miles and didn't have the right tool to remove the filter - so, the oil level is at the top of the allowed maximum. Thinking this cold be another cause. Thanks in advance...Jeff ---------------------------------------- If the new plugs get you back on the trail run it hard this will help burn off some of the carbon on the upper piston ring then recheck new plugs for correct color (local shop pulls them on the dyno to help seat the rings and prevent carbon scoring. What oil did you put back in your xp? When a spark plug does not fire correctly then the unburned fuel goes into the oil pan plus deposits black carbon on top of piston and rings. NOT GOOD!

 

Thanks for all the great info. I put in the recommended Polaris oil (from the oil change kit). I did not check for spark yet - I'm sure it's the plugs (I hope). I will let you know when I get them in a couple days. I thought you could clean plugs up with gas and they would work fine - I'm glad you corrected me - seeing it didn't work...Thanks again...Jeff

 

Need to get the oil filter changed, no use changing oil if you dont change the filter.

 

If I recall correctly, there is a computer re-flash that sets the idle a little higher in an effort to keep the plugs from fouling. The re-flash may also change some other parameters too. The plugs fouling on the 850 is a common problem. Ditto on letting the machine warm up, even if you are just going to move it a short distance...that helps keep the plugs from fouling.

 

Ya - I hear ya, I didn't want to stick a screwdriver in it and rip it out without the right tool. Especially since it's recessed in the skid plates. I don't min dropping a few more bucks on more oil - only helps with the early break in.. Thanks.

 

You could get creative and install a plate over the oil filter access hole to keep from punching a hole in it like my buddy did.

 

I have the very same problem (filter wrench) and fouling plugs i have changed the plugs and the oil and the air filter (K&N) and i tried it again today and another really crappy start i have had the reflash and i know its gettting cold here but it should start better for a new machine nno????