800 EFI Engine problems - Polaris ATV Forum
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post #1 of 14 (permalink) Old 06-03-2013, 07:09 AM Thread Starter
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800 EFI Engine problems

I recently had the Camshaft and lifters go in my 2011 sportsman 800 EFI at 151 hours and a little over 2k KM it (about 1000 miles). The machine was of coarse out of warranty so I decided to do the fix myself, I have been working on small engines all my life rebuilding many motorcycles snowmobiles and ATV's so it was not a big deal to me.

Of coarse i purchased a service manual before taking on the task.

First I will tell you that you CAN do this without pulling the motor but the 2 head bolts will give you a bit of a problem to get out. I wont go into the details oh doing the job but I wanted to let everyone know what I am going through with this machine.

When installing the CAMSHAFT the service manual clearly states to use the dots stamped on the gears for timing, there is no other way to do this and if the dots are lined up then there is no way it could be out of time. well in my case they were WRONG .. in going by the dots the engine ran like crap back firing through the intake. I then tore it down again to double check the mark alignment and doubble check the service manual, I put it back together again with same result. the third time I took it apart i noticed a spot of red paint on one of the teeth on the crank gear. I decided to try that tooth instead of the one with the DOT on it and it ran perfect.

After going through that it worked like a new one again .. but that was short lived .. I ran the engine 5 hours and changed the oil and filter .. then again at 15 hours (to make sure there were no filings left in the engine anywhere)

Now I have an issue that the first start of the day (after setting all night) it will start up and idle normal .. however if you touch the throttle at all it dies immediatly .. then the engine had 0 compression in both cylinders . after setting for 15 min or so it will start up again .. this process will repeat unless you let the engine idle and warm up for at leaf 15 min (way too long). then it will Work like a new one all day long with no issues and has 180psi compression in each cylinder.

I have sense taken the head off again and checked all the Valves and springs, there are no bends and they all move as normal . I would say it seems like the cylinders are washing out but the plugs are dry when this happens and if you leave it idle until the fan kicks in then it doesn't do it.

Anyway im still troubleshooting this (next step is maybe planing the head) I think it might be leaking a bit of Antifreeze in the jugs from the head gasket when it sets.

Oh and by the way ... Polaris claims to not have any issue with the CAMS in these engines .. yet I know of another machine like mine within 10 miles that had the same issue and the CAM was on back order for 4 weeks when I ordered it.
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Last edited by neal860; 06-03-2013 at 08:43 AM. Reason: Adding Photos
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post #2 of 14 (permalink) Old 06-03-2013, 05:49 PM
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Welcome to the board!
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post #3 of 14 (permalink) Old 06-03-2013, 06:13 PM
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Hmm...problem with the compression release? or perhaps hydraulic lifters sticking till warmed up?
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post #4 of 14 (permalink) Old 06-03-2013, 06:44 PM Thread Starter
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I was thinking the lifters might have been sticking too ... but i tried this in the morning withe the valve cover off and can see all the rockers moving normal.

I didnt know there was a decompression on these .. is there?

Thanks for your input

- Neal
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post #5 of 14 (permalink) Old 06-04-2013, 10:59 AM
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Just from a car stand point it sounds like you have way too much cylinder clearance when cold and as the eng finally starts and warms up the clearances get tighter so it starts ok when finally warmed up.

2006 800EFI just stock stuff
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post #6 of 14 (permalink) Old 06-04-2013, 12:04 PM Thread Starter
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I havent checked the clearance on it yet as i didnt pull the jugs completely off, I figured it was washing out somehow.

Also these engines are strange in the fact that both pistions are side by side instead of staggered

But I can go out cold and it has 180psi on compression test ... I will have to make a video and post it .. its a strange beast

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post #7 of 14 (permalink) Old 06-07-2013, 05:08 AM
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If it has 180 cold no amount of gas would wash the cylinder walls enough to cause no compression. You have to have some mechanical problem causing no compression(broken cam etc.) or you have compression all the time and some other problem.

2006 800EFI just stock stuff
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post #8 of 14 (permalink) Old 06-07-2013, 10:41 AM
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Oil pressure relief sticking can cause things like this, also could help to explain such early wear in cam and lifters.
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post #9 of 14 (permalink) Old 06-07-2013, 05:37 PM
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Hi, if you need top end parts, I have an 800EFI junked.
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post #10 of 14 (permalink) Old 06-21-2015, 03:43 PM
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I too had a 800 polaris engine eat it cams and associated parts it was in a 2011 6x6 dealer said polaris had problems with burs in the oil pressure regulating valve polaris stood the valves and cylindars but would not stand any more. I was told that polaris was aware and had a stop sell order anyone have anything to offer
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