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Polaris Scrambler XP Discussions for the all new 2013 Polaris Scrambler XP 850

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post #1 of 12 (permalink) Old 05-23-2019, 03:02 AM Thread Starter
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Blown Motor

2013 850, bought it brand new in April 2013. Followed maintenance to the letter, serviced every 100 hours, (about a year and a half). K&N air filter, Polaris extreme duty oil change kits. Basically stock, with a few body mods (armor, fender flares..).
Having trouble with it starting, thought it was the throttle positioning sensor (tps). Send it in for the change (has the original tps) and after a good look over they find that the compression in both cylinders is around 100psi when it was supposed to be 200psi. 5500 miles on it. They think it’s the rings and will know more once they start tearing it down.

I’m a northeast rider, not a big water or mud fan but have done it. Lots of dust up here.

Looking for thoughts on what happened and how to avoid another 2000.00 bill in the future!

Last edited by JohnJr; 05-23-2019 at 05:12 PM.
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post #2 of 12 (permalink) Old 05-23-2019, 03:51 AM
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Just my opinion, but I would look into another air filter & get rid of the K&N. Most would say to service it at least once a year too.

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post #3 of 12 (permalink) Old 05-23-2019, 04:50 AM
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Before reading the last reply I can promise you the KN air filter is your problem. Check the air filter tube after the air filter for dust.


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post #4 of 12 (permalink) Old 05-23-2019, 06:53 AM
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Originally Posted by Liftedpsd View Post
Before reading the last reply I can promise you the KN air filter is your problem. Check the air filter tube after the air filter for dust.


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I second this, I got my 2010 from a guy that had a K&N in it when i bought it. Did lots of research and the first thing i did was buy a OEM Polaris filter.

Saw lots of People getting blow by with the K&N, Most in dust were using OEM or UNI, Most having the best luck with the UNI with dusty conditions.

Good Luck, and thanks to this forum and others for Great Info!!

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post #5 of 12 (permalink) Old 05-23-2019, 07:37 AM
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Yes, K&N filters are bad for rings especially in dusty conditions. The filter need to be serviced properly about once a month depending on conditions. If you ride in a group and ride for a few hours every weekend, the filter should be serviced after each ride. If you use a pre-filter sock, the sock needs to be cleaned after each outing, but the filter may not need servicing for a month or so. If you intend to stay with K&N, it's best to have 2 filters; one in and one ready to go in. Proper servicing takes about a hour or two using the K&N filter service kit. K&N's flow more air, but unfortunately they flow more dust too. Those fine particles of dust can wear out rings in a relatively short time. Extreme example: I bored a cylinder, installed a new piston and rings into a Yamaha 100 for a kid who was racing motocross. He didn't have the money for a new air filter, so he taped about 4 layers of an old nylon stocking over the inlet bell of the carb. He raced two semis and a final the following Sunday. On Monday he was back at the shop and said after he finished the moto, the bike died and he couldn't restart it. It had no compression - I took it apart and it needed bored out again - the rings were paper thin on the intake side - I told him I would not fix it again if he did not put a good filter in it - I fixed it and it wasn't too long after that the crank went bad - it was never fixed after that.
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post #6 of 12 (permalink) Old 05-23-2019, 08:34 AM
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Yep, K&N = its been dusted and the rings are gone.
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post #7 of 12 (permalink) Old 05-23-2019, 05:11 PM Thread Starter
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I would clean the filters about twice a year, prefilter and filter, dry and reoil. Would take me an overnight so it would dry well before I oiled and reinstalled. I also use a little filter grease where it seats into the box. Very surprised by all the comments, does get me to thinking. I will have the shop check the line from the box to the intake.
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post #8 of 12 (permalink) Old 05-28-2019, 12:10 PM Thread Starter
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Update! Just spoke to the shop, problem was NOT contamination from poor filtered air. It was a spun timing gear! This is an older machine, they had pressed the timing gear on instead of welding them like they do now. Will have her back later this week!
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post #9 of 12 (permalink) Old 05-28-2019, 01:38 PM
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So you are telling us the shop that diagnosed the 'blown engine' made an incorrect diagnosis? How far did they have to tear the engine down before they realized it had slipped time? Do they propose to re-time it and weld the gear in place without complete engine disassembly or are they going to replace the crankshaft?

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post #10 of 12 (permalink) Old 06-11-2019, 03:54 AM Thread Starter
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The leak down test after the original compression only test started to indicate a different problem. When they took the head off they found valve impact marks on the pistons, first clear indication of the slipped timing gear. They had seen this once before. They did a complete tear down, checked the valves, reseated, replaced the pistons and welded the timing gear back on the crank after checking for chips and cracks. Basically freshened up the top end of the motor. Here is a pic of the crank. You can see the timing marks are misaligned.

Have it back and it feels much better, must have been at reduced power for a while, but slowly, so never noticed it. Big ride in Maine this week. Will see how she does.

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