Polaris ATV Forum banner

1 - 20 of 52 Posts

·
Registered
Joined
·
26 Posts
Discussion Starter #1
Hey Guys,

Sorry to beat this dead horse, as I did use the search feature and found many users with a similar backfiring problem on an 850 xp and adjusting the throttle cable seemed to fix. I did that procedure and mine is still doing this. My quad is a 2009 850 XP, very well maintained machine. 131 hours of use. After a few months of sitting in the garage I went to fire it up for hunting season yesterday and took it for a spin.

At idle it's missing, making a slight "popping" or "burping" sound occasionally as it burps or misses at idle and it's backfiring very loudly consistently on decel. Can't do much hunting with gunshots following me around, lol. It also just seems like a loss of power too.

After adjusting the cable, the problem still occurs. So i added a zip tie in between the contacts. Same problem. I then took off the plastics and found this:



Here is a further back photo so you can see where it is...



Looks like a god damned mouse chewed the wiring!!!! I think this might be the source of the rough running/backfiring. How should I go about fixing? Just electrical tape and call it good? It doesn't look like they made it all the way through any of the wires.

Do you agree this could be the issue?
 

·
Registered
Joined
·
522 Posts
Something like that could definitely cause all kinds of gremlins I would think. You could try and tape it. Check each wire individually and tape each wire over any damage, then bundle the wires back together and tape the harness back up good. Won’t hurt to try.
 

·
Premium Member
Joined
·
7,483 Posts
I would be inclined to believe that's the source of your problem.

To fix those wires I would pull back the loom and separate the wires. Fan them out nicely and clean the damaged ones. Then put liquid tape to the bare spots. I would apply two coats allowing enough time to dry between coats. Then I would tape those spots as a final step.
 

·
Registered
Joined
·
26 Posts
Discussion Starter #4
Thank you for the suggestions gents! I'm off to Canadian Tire for some liquid electrical tape. I'll report back if this fixed my issue to benefit any others searching the same/similar issues.
 

·
Registered
Joined
·
26 Posts
Discussion Starter #6
I think I would try to remove the mice in the garage also!
Oh, I am!!! Got a bucket trap out right now, set it last night and got 3 overnight. We're constantly battling these things.
 

·
Registered
Joined
·
26 Posts
Discussion Starter #7
Well, I got the wires exposed and put on liquid electrical tape but it doesn't seem to have solved the issue? Here is a video, you can hear the rough idle and what sounds like a frequent sputter from something.


Any ideas?
 

·
Registered
Joined
·
720 Posts
You say it has set awhile in your garage and not been run right? Did you put fresh gas when you started it, or does it have old gas in it?
 

·
Registered
Joined
·
26 Posts
Discussion Starter #9
Hey SteveC25,

Yes, it had some gas that was a few months old (maybe 1/4 tank) and then I filled it right up with fresh mid-grade gas (89 octane). I took it for a 5 min burn up to the end of the road and back thinking it might have cleared it through the system but nope it's still doing it.

I just checked the plugs

#1. (closest to front) was really white and smelled of un-burned fuel.
#2. (closest to back) was normal black and smelled of un-burned fuel.

Not sure what to do. Dealer is a few hours away and I can just imagine what they'd charge for this, a there is no check engine light or anything. I just want to go hunting, lol.
 

·
Registered
Joined
·
1,106 Posts
Hey SteveC25,

Yes, it had some gas that was a few months old (maybe 1/4 tank) and then I filled it right up with fresh mid-grade gas (89 octane). I took it for a 5 min burn up to the end of the road and back thinking it might have cleared it through the system but nope it's still doing it.

I just checked the plugs

#1. (closest to front) was really white and smelled of un-burned fuel.
#2. (closest to back) was normal black and smelled of un-burned fuel.

Not sure what to do. Dealer is a few hours away and I can just imagine what they'd charge for this, a there is no check engine light or anything. I just want to go hunting, lol.
white plug is not good, it can be antifreeze in cylinder or a lean air fuel mixture, usually lean air/fuel is grayish color on plugs and that's usually really not good. Did you check if you have a good spark on plug that was white and smelled fuel in cylinder. ?
 

·
Premium Member
Joined
·
7,483 Posts
On the earlier XP's a lot of guys switched to NGK iridium spark plugs with success in curing the mis and backfire.
 

·
Registered
Joined
·
26 Posts
Discussion Starter #12
So I went out and tinkered with it this morning a little more...

#1. Yes, both plugs are getting a good spark.

#2. Not sure it's a head gasket leak, as the coolant mark is just below Min. and I've never had to add Coolant.

#3. I continued removing plastic and found a tiny rub on a wire under the steering plastic. I traced it back to the thumb throttle. While the wire was rubbed and a tiny portion exposed (like a pinhead), it wasn't touching any metal or anything else (rubbed on plastic). Fixed with liquid electrical tape but I am not sure this is the issue.

I have included a photo of the plugs. Might be time to replace them as they haven't been.
 

Attachments

·
Registered
Joined
·
26 Posts
Discussion Starter #14
Here is a video of it running this morning... Upon startup it runs good for about 30 seconds. You can hear the first burp at about 25-26 seconds. Idle RPM seems to be okay, but it jumps around when it misses or does its little bog.

 

·
Registered
Joined
·
26 Posts
Discussion Starter #17
The white color indicates lean, or lack of fuel.
Which could mean many different things, I guess. I'm picking up some new spark plugs later this afternoon and will try that, then I guess the next step is to inspect the throttle body. Maybe it just needs to be ridden a bit more after sitting for a few months?
 

·
Registered
Joined
·
26 Posts
Discussion Starter #19
It appears to be getting fuel in both cylinders... I had both spark plugs out and was turning over the engine and a good atomized spray was coming out of each cylinder. I am not sure what the issue is. If it was not getting fuel, do you think it would idle within spec? Confusing!! Hopefully new plugs might fix it, I'll know in a few hours. Not sure how to test or troubleshoot the injectors, that might be beyond my skill level.
 

·
Banned
Joined
·
2,959 Posts
Ok it's getting fuel.

I'm confusing you. Lean is getting fuel, just not enough of it. That's what the white plug is indicating. Not getting enough fuel with the same amount of air, each stroke, makes it burn hotter.

If it wasn't getting fuel plug would probably be black. You want a brown/tan plug

Confusing I know. Less fuel = hotter combustion.

Can you tell if they are getting the same amount of fuel. May not be noticeable but maybe it is.

For a test you could switch the injectors and see if the white plug follows the injector.

Or just take them out and gave them cleaned/ flow tested.
 
1 - 20 of 52 Posts
Top