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Discussion Starter · #1 · (Edited)
I picked up a 2018 Polaris Sportsman 450 EPS with only 145 miles on a trade. The thing looks practically new, but it runs and drives rough. Engine makes a screeching noise st idle and when starting to drive slowly it gets really loud. The seller said he thinks it need the bottom end rebuild. It only has 145 miles on it. Could it really need a new bottom end at only 145 miles? Any suggestions on how to diagnos this? Has anyone had to replace or rebuild a bottom end on a new ATV? Any idea what could cause a bottom end issue on a new ATV? I'd greatly greatly appreciate any advice. Thanks!!!!
 

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19’ 850SP Camo. MtAiry Maryland
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I picked up a 2018 Polaris Sportsman 450 EPS with only 145 miles on a trade. The thing looks practically new, but it runs and drives rough. The seller said he thinks it need the bottom end rebuild. It only has 145 miles on it. Could it really need a new bottom end at only 145 miles? Any suggestions on how to diagnos this? Has anyone had to replace or rebuild a bottom end on a new ATV? Any idea what could cause a bottom end issue on a new ATV? I'd greatly greatly appreciate any advice. Thanks!!!!
Noooo.....and even if it were run low in oil, the top end would wear out first.....make sure you check all the fluids and make certain you have fresh non ethanol fuel in it.
 

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Discussion Starter · #3 ·
Noooo.....and even if it were run low in oil, the top end would wear out first.....make sure you check all the fluids and make certain you have fresh non ethanol fuel in it.
Thanks for the advice. I'm going to clean out the tank and put fresh non-Ethenol fuel in it now. Will revert back.
 

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19’ 850SP Camo. MtAiry Maryland
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Thanks for the advice. I'm going to clean out the tank and put fresh non-Ethenol fuel in it now. Will revert back.
Sounds good,...that just might take care of the “rough running”. —Also...I see it’s a 450, they foul plugs often, get an NGK Spark for it as soon as possible.
 

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2018 Polaris 850 SP Camo
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Thanks for the advice. I'm going to clean out the tank and put fresh non-Ethenol fuel in it now. Will revert back.
Revert back to what? Did you mean report back? What MrED said. Make sure it has fresh fuel. Put in a new plug and make sure that air filter isn't clogged and no mouse nest in the air box. Those are easy things to check first.
 

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2008 800 ho efi, 2019 850 SP premium
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Thanks for the advice. I'm going to clean out the tank and put fresh non-Ethenol fuel in it now. Will revert back.
Welcome to the forum

Your question has now been logged into the queue and the next available forum member will answer you shortly
 

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Discussion Starter · #7 ·
Revert back to what? Did you mean report back? What MrED said. Make sure it has fresh fuel. Put in a new plug and make sure that air filter isn't clogged and no mouse nest in the air box. Those are easy things to check first.
Sorry I meant to type report back. I'll check the air filter, and order a NGK plug. I forgot to mentioned Engine makes a screeching noise at idle and when starting to drive slowly it gets really loud.

Thanks again everyone for the advice. This is truly appreciated!!!
 

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19’ 850SP Camo. MtAiry Maryland
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It might be a good idea to post a video of that noise you speak of....you’re going to get the most honest answers here.....we want to help you, not make a dime off you. 👍🏻
 

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2018 Polaris 850 SP Camo
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Sorry I meant to type report back. I'll check the air filter, and order a NGK plug. I forgot to mentioned Engine makes a screeching noise at idle and when starting to drive slowly it gets really loud.

Thanks again everyone for the advice. This is truly appreciated!!!
I was just funnin ya! Post a video of the sound. Could be something internal wrong. Wouldn't be the first machine off the showroom floor to crap out out with little miles.
 

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Discussion Starter · #11 · (Edited)
When I got the machine, the oil was right up to the line that says add oil. I'm going to add oil and see if that makes any difference, though I dought it. I don't know if the previous owner submarined it. My guess is no, because this thing looks pretty clean.
I posted a video to vimeo of it running and you can hear the screeching noise. Let me know if for any reason you can not see the video or if I should film anything else. You guys are amazing!!! Thanks everyone!!!!
 

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2021 Sportsman XP1000S
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Holy cow ?!
 

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Discussion Starter · #14 ·
Given that I don't know when the oil was last changed, It's probably better to do a full oil change, but does it pay to do it if the engine or bottom end may need to be openned up? Maybe better to wait till I figure out what's wrong. Also forgot to mention that it seems to shift between P/R/L/H pretty easily. I haven't driven it more than about 1 MPH because I don't want ot risk causing more damage. The screeching noise kind of sounds like a belt slipping.
 

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1995 magnum 425 4x4 2019 sportsman 570 2020 sportsman 850
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How are the motor mounts? Sounds like it might be rubbing on the outside of the engine to me. You could always send an oil sample off, $30 and a few weeks to get results back
 

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Discussion Starter · #16 ·
RECAP RECAP RECAP

To make it easier for everyone, I'll recap so no one has to go through all the history.above.
1. Got a 2018 Polaris Sportsman 450 H.O. EPS on a trade. It only has 145 miles on it.
2. Original owner said he thinks it needed a new bottom end or bottom end rebuilt
3. The ATV starts up fine, idles and drives at least at 1 or 2 MPH. Haven't tried it any faster as I don't want to cause any more damage.
4. Seems to shift between P/R/L/H no problem
5. Engine light is off.
6. When I received it oil level was right up to the line that says ADD OIL. Wiped the oil on white paper towel and the color looked clean but like a clear greyish color, not the typical honey brown color I am use to seeing oil in cars. Might be because this is a Polaris oil color.
7. Engine screeches when idling and gets louder as RPMs go up. A sound almost like a belt slipping.
8. Opened the airbox and there was some splats of bud on the walls. Did look it was ever filled up with water.
9. Pulled the clutch air duct inlet and felt inside and it seems like there was some oil or dirty water on the walls of it.
10. Noticed that the previous owner had opened the outer clutch ASM-cover, because the cover was missing a few screws.
11. I don't think it was underwater, but not completely 100% sure.
12. Motor mounts look to be OK
13. The air filter looked pretty clean, but I still washed the outer jacket. I topped up the oil with Polaris oil. I am ordering Oil, Filter, NGK spark, new air filter, missing screws for the outer clutch ASM-cover, and anything else anyone recommends I should order/replace/service, I'm going to empty the tank and fresh ethenol free gas.

First Video - You can hear how she runs

Second Video - taking it apart

Motor Mounts
151811

151812
 

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2018 Polaris 850 SP Camo
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Dust and a little crud inside the air box is normal. The pre filter and filter stops it from going any farther into into the engine. When I clean or change my pre filter and air filter I always clean the air box.
 
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