Hello, John Talley here with partzilla.com.
Today I'm going to show you how to do a compression test on our 2011 Polaris Sportsman 850.
Not a lot to it.
Basically it's no more difficult than replacing the spark plugs.
All we need to do is pop off the seat, pull a couple of panels and get them out of the
way, and get the test done.
So let's get started.
First let's go ahead and get the seat off.
All you have to do is pull on it from the center kinda hard and she'll pop loose.
Now you do want to do this test warm.
I've actually already warmed up the engine enough to get this done, so we can go straight
into putting the compression tester in there.
Next, let's go ahead and get that panel out of the way.
Now if you don't already own a set of Torx, you'll need to buy a set, because Polaris
loves using them.
A Particular one is the T-27.
Alright, once you've got that Torx out, you just have one, two, three of those plastic
rivets that need to be removed.
Alright guys, next you want to get this shifter out of the way, which, on this particular
unit, somebody has broken it.
Here's what you should have done to do it.
Remove this outer cover, and then there was a Torx in there that needed to be removed
and then she would have just pulled right off.
It looks like I'll be replacing that.
That exposes the side of the engine, and gives us easy access to the spark plugs.
Need a thin-walled 14mm to get in there.
Like I said, I've had the engine running for a while, so you're going to want to use a
magnet to get those out of there because they're going to be a little bit warm.
Burning pretty rich.
Same thing.
It looks like she's burning oil to me guys although it isn't smoking.
So, we have our adapter on.
Pop it in there.
Don't get carried away on tightening it down too much otherwise it isn't going to come
back out.
Now what we're looking for is each cylinder to be about within 10 percent of each other,
and the other factor we're looking for is we want to see an overall compression in between
210 and 250 psi per cylinder.
Alright, we've got our tester hooked up and the process here is to turn it over about
six or seven times with the throttle held open, but with the Polaris you have to be
holding the brake as well.
I've only got two arms, so I've got my assistant.
Let's see what happens.
Throttle open.
Alright.
On that front cylinder we're almost to 200.
A little on the weak side.
Alright let's go to that back one and see what we've got.
Throttle open, brake closed.
Alright.
Here's going to be the trick on this one.
She only got to about 165.
So, that is a huge difference in between front and rear, so we've got something going on
in there guys.
So, this one is going to be a pretty short video to start with.
So from this point on, like I said, we're going to start exploring what's going on inside
this engine so this is just the beginning steps of determining which steps you should
take in trying to figure out what the problem is.
So if you would, come back, find us on our YouTube channel and find out what's going
on with this engine.
Until then, I want to say thanks for watching.