Polaris ATV Engine - Is it Time For a Rebuild?

Does a certain amount of mileage call for a rebuild on a Polaris ATV engine? A compression test might give you some answers, and so can our resident powersports expert John Talley.

John does weekly Q&A livestreams on our YouTube channel every Friday at 3pm Eastern. In this edition, John answers a couple of questions about whether a rebuild is necessay for a Polaris Sportsman 850 engine. 

Polaris Sportsman 850 rebuild

Polaris ATV Rebuilds

My 2016 Polaris 850 has 25,000 kms. Would you suggest a rebuild soon?

John Talley: No. No, I mean unless it’s acting strange, you keep going. We’ve got a Kawasaki Mule PRO FXT that I did a little work on this week, and it runs in between two of our primary buildings at this location. There’s another building about 1,200 feet away and that machine has 21,000 miles on it, and I did a compression test on it and it looks fine. And all we’ve done to that thing is put a couple of belts on it, three sets of tires, and just oil and plug changes and oil filters and that’s it. And air filters, and that’s just your basic maintenance and that thing is still running strong. So no, just because it’s a high mileage machine, it doesn’t bother me at all unless the compression numbers are looking off or starting to sound funny, I wouldn’t change the thing. If it rides great and there are no metal shavings in the oil, just keep going. At 25,000 kilometers, it just may be getting warmed up. 

Check out the playlist above for our complete Polaris Sportsman 850 top end rebuild series, starting with the compression test

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My Polaris 850XP starts, but with a slight rev you can hear a knock. Would a rebuild kit save the motor?

John Talley: I don’t want to caution you here but it’s probably not the engine what you’re hearing. What you’re probably hearing is knocking of the primary and/or secondary sheave in the clutch and the belt housing. When those weights and pivot points and springs and shafts start to get worn, when the belt’s just sitting there, when you rev it up, when it activates, it’ll clack. You’d swear it’s going to be in the bottom end but chances are it’s probably somewhere in your clutch system, whether it be the drive or the driven clutch. So, I believe we have a video of an older 850 XP that we replaced the clutch on that shows you how to remove the cover. So just go in there and take the cover off, crank it up carefully, glasses on, and take a listen then. I bet you that’s where you’re going to hear the noise coming from.  

Watch the video above to see how to rebuild the clutch on a Polaris Sportsman 850.

Want to see more live repair questions answered? See more motorcycle and ATV repair questions answered here.  



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