12´pro rmk 800 running on one cylinder.

prormk12 · Dec 14, 2014

12´pro rmk 800 running on one cylinder.

hello! i have a problem with my 2012 pro rmk 800.. it´s running on one cylinder. It ran fine after the last trip i had with it, last year) So i delivered it to a polaris dealer to check what the problem was. They said that the compression was low.. 116psi, and that it SHOULD be around 159psi?? is that true? anyways, i changed pistons, and checked compression,All good.. Fired straight up after 3 pulls.. Sounded like it was running fine!
I tested it for about 5 minutes that night, and it all seemed good. The day after, the problem was back.. Started it up, and it was running on one cylinder again. Checked compression, spark, fresh fuel. Didn't help.
Its like it wants to run on both just when I'm starting, but after one sec its running like ****. Anyways its seems like the other cylinder "kicks in" at around 5000rpm, and then it runs fine. But as soon as rpm is under 5000. Its running one one again.. i have only seen the check engine lamp for a couple of seconds. The codes was:
-"trottle release signal, trottle stuck",
-"trottle position sensor, abnormal rate of change"
but after a restart, it never came up any more lamps.

Here is a video of the problem: https://www.youtube.com/watch?v=bas-ynmRD6s&list=UUkGdL0agA8TEJUmye3fuRIQ&index=1 bad quality video, but you can hear the pro side cylinder kicks in at about 5000rpm.

hoping you guys could help me

seth25 · Dec 14, 2014

Sounds like injectors.

nosman4 · Dec 14, 2014

I was gonna say the same thing, if you got any question swap the injectors side to side and run it again. Should be pretty easy to tell if it switches cylinders.

prormk12 · Dec 14, 2014

ok! then i will just try to change the injectors first. thanks for the help!

89sandman · Dec 14, 2014

First I'd check the Fuel injector wiring at each injector plug to make sure both sides strobe. If they do then I'd pull the plug wire on each side and see which one is running at lower rpm's and then swap injectors and see if the missing cylinder moves to the other side. If it does you have a bad injector.

beamslayer · Dec 15, 2014

159 is this engine stock . I would say 125ish .

jeb338 · Dec 15, 2014

Dead cylinder

Have the same machine with the same problem. When I watched your video mine was doing the same thing took it two the dealer several times they could find nothing wrong when they would hook it up to the computer give me some new plugs and send me on my way. As soon as I would get back on the snow it would act up again sometimes right away sometimes it would take a 1/2 mile. Replaced injectors and coils still had the problem this time when it happened it was dark and when I pulled the side panel and hit the throttle I saw a spark on the frame where the wire was zip tied to the tube. Went to napa in the morning bought two pieces of plug wire screwed them and problem was solved. Check your wires and make sure that they have not wore through or buy two pieces and screw them in for a quick cheap check.

prormk12 · Dec 16, 2014

Will check plug wires tomorrow. Thanks alot for the help!

towny · Dec 16, 2014

I had the same “Running on 1 cylinder” that you describe on my 2011.
I replaced everything chasing it down until I finally had to tear it down!
Reading just about everything I could find on similar problems, there’s a lot of things
that can cause similar running symptoms, such as, a broken reed, bad injector, bad crank shaft seal etc.!
Have you blown a belt recently! Might take your clutch off and check the seal if it’s missing on the PTO cylinder.
Started with the simple things trying figure it out. No luck so started tearing into it.
If you finally run out of “simple fix” options it’s time to look deeper.

The problem with mine ended up being a badly scuffed/gouged piston skirt on the intake side?? Not sure what caused it! The exhaust side had some scuffing that I could see by removing the Y-pipe so I went ahead and did a tear down and found the piston skirt was really bad on the intake side.
Funny thing is the compression was still good! I guess, since the damage to the piston was only on the skirt leaving the top of the piston and rings still looking good. Good enough to seal keeping the compression up?
With a bad piston skirt it won’t seal the ports well enough to get a good charge into the combustion chamber especially at a lower RPM! As you rev it up, it finally creates a good enough charge to get it to fire. There’s more to it but in my case it was a bad piston causing the running symptoms you describe.

prormk12 · Dec 17, 2014

Yes, but i just replaced old pistons( which were still in good condition) with wössner pistons. And the cylinders were in really good shape! So i doubt the piston skirt is damaged, and also the problem were there before the piston change.
I tried new spark plug wires and boots today, but still 1 cyl.. the sparkplug on PTO is wet, and i got spark.. is it possible that the injector just gives it too much fuel?
I didt got time to check for more possible problems today. But on friday i will try to switch the injectors, and see what happens.

Leftys · Dec 17, 2014

What's the condition of your Reed Valves?

towny · Dec 17, 2014

Oh sorry, I didn't catch that you replaced the pistons!:face-icon-small-sho
If all else has failed? It could be possible the injector is not controlling the fuel like it should but if you did as others have suggested and still have the problem. It still sounds like the crank case is losing pressure when the piston travels down!? It doesn’t get enough charge of air to mix with the fuel which will "wet" foul the plug!
Try this. Take the plug out and dry it off or put new plug in. It probably?? will fire up and run on both cylinders for a little bit then go back to the same ol miss. If this happens I'm pretty sure it’s the reeds or a bad PTO crank seal not sealing.
Pull the clutch and removed the seal cover to check the seal?
You may need to do a leek down test if visually you can’t see anything?
It would be much easier if it were the reeds but it's still a job to get too them!
The rubber boot of the reeds could have a crack in it which would do the same thing!

Sure hope this helps ya get the problem solved, just gota keep checking things (going deeper) till you find it!

prormk12 · Dec 17, 2014

will check crank seal and reeds! but the sled only has 350 miles on it, so it would be kinda strange if the reeds already is chipped?

towny · Dec 17, 2014

Hummm. Yeah your right. With only 300+ miles youl'd sure think the reeds and crank seal should be good! But if you blew a belt and the cord got wrapped around the crank? it can easly take the seal out for sure!
The reeds are a pain to check. Quite a bit of disasimbly to get to them!
Have you gotten a chance to try what 89Sandman suggests doing with the injectors? Sure could be it?
Guess other then what's been suggested I really don't have any other ideas for you.:noidea:
Try the "drying the spark plug" deal I suggested and get back to us.

Leftys · Dec 17, 2014

It always amazes me at how the mechanical items are looked over before proceeding to other circuits of making an engine run. The way the engine acts and will not run down low, but once you get the RPM up will fire on that hole really sounds like reeds are skeptical. It may have low miles and low run time, but anything can break new included. They are a pain to get to for a simple inspection which really does sucks. Bummer you are having issues.

prormk12 · Dec 17, 2014

never blew a belt.. I'm gonna check all the possible causes on friday

will be back with more info

tuneman · Dec 17, 2014

Before you go tearing into reed replacing, just pull the airbox and look for an oily film on one of the throttle bodies, around the bore or on the throttle plate. If clean, it's probably not reeds. If oily, you may have a reed issue.

prormk12 · Dec 19, 2014

Soo! Today i switched the injectors side, and replaced sparkplug cables and sparkplug caps.. started the sled, and it was firing on both cylinders again! Took a test ride, and it ran just perfect.
BUT.. when i start the sled, it idles at 1750rpm. But as soon as i touch the throttle, it will idle at 2300-2400rpm, and it wont go down untill i restart again.. and also the PERC button doesn work. Nothing is happening.

I also have a problem that the check engine lamp with code 520 194 7, turns on at idle, the sled will then cut, and die if i dont rev it up a little. I got it on tape: http://youtu.be/TX1nELM4L3Q
Any ideas?? :noidea:

mike_s · Dec 19, 2014

So, after having a DTC relating to the tps, no one thought to see if it was out of adjustment or faulty? Seems I would have started there before spending money on pistons and all this other stuff...

Sent From God Knows Where...

prormk12 · Dec 19, 2014

Well, i just trusted the dealer

12´pro rmk 800 running on one cylinder.

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