HELP!!!! polaris 500 knock after rebuild - Polaris ATV Forum
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post #1 of 15 (permalink) Old 06-23-2019, 10:20 AM Thread Starter
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Thumbs down HELP!!!! polaris 500 knock after rebuild

I do understand this is more of a Quad form but from what I understand the 500 engine has been in use for some years and in different platforms.

anyways.

I have a 2005 polaris ranger with about 8XX hours on it. it was purchased from the original owners who only used it around their house and at their hunting club. about a month ago I was out in the forest doing some fairly hard riding when it developed a knock.

I tore down the engine, and didn't find anything too concerning besides on the balance shaft and oil pump a tooth or 2 had some slight chipping.

I replaced OEM crank, OEM balance shaft, OEM oil pump, all with OEM bearings. a "niche" cylinder kit, a new bendix, and bendix bushings. I lapped the valves exhaust valves looked fine, intake valves had a small burr around them. and the exhaust rocker has a gouge on it from the decompression ball.

now I did reuse the timing chain, timing sprockets, head, cam, rockers.

there is no clutch on the engine right now so that can be eliminated. the timing chain has a little less than a 1/4" of slack in it on the side that doesn't have the tensioner. I can not see any flopping around with the side cover off and the engine running. the valves are also correctly adjusted.

i'm completely lost at what else could be causing this noise. I understand that these 500's are just noisy engines, but this doesn't seem like a "normal" noise.

link to video of the knock-
the smoke in the video is from oil that spilled on the manifold from running it without the valve cover on it.

any info or possible things to look for would be greatly appreciated!!!
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post #2 of 15 (permalink) Old 06-23-2019, 12:46 PM Thread Starter
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*UPDATE* so I tore the engine back down..
and I noticed a little plastic plunger with a rubber tip i'm assuming it's an oil pressure regulator of types? maybe i'm starving the engine of oil???
the pic with the screwdriver shows the location of this plunger, it is accessible from outside the engine. behind a 12mm bung in between the hard oil lines.
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post #3 of 15 (permalink) Old 06-24-2019, 08:20 AM
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Yeah, that's the one-way valve #16 in the pic part number 3086810 that acts as a oil pressure regulator. Its supposed to have a spring on it under the plug.
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post #4 of 15 (permalink) Old 06-24-2019, 10:34 AM Thread Starter
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could a damaged one way valve cause some oil starvation and noise?
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post #5 of 15 (permalink) Old 06-24-2019, 10:56 AM
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Quote:
Originally Posted by coolcrushicekilluh View Post
could a damaged one way valve cause some oil starvation and noise?
I suppose it could. I was looking at your parts list. What about piston/rings/wrist pin? Were they replaced? If not is there any play in them? Any scuffs on the piston skirt? Good and tight in the bottom?
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post #6 of 15 (permalink) Old 06-24-2019, 11:20 AM
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Op, I've been thinking about your build and since you put a new crank, balance shaft and oil pump in, did you double check shaft end play? Excessive end play of the shafts will cause a knock in those engines when newly rebuilt.
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post #7 of 15 (permalink) Old 06-24-2019, 11:24 AM
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I should also clarify on the one-way valve, it primary function is to prevent oil from the tank draining into the engine. I think it also regulates pressure too but not positive on that part.
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post #8 of 15 (permalink) Old 06-24-2019, 12:14 PM Thread Starter
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@polman500
huh, funny that you mention end play. I was actually out in the shop a few min ago checking my end play and from what i've come up with i'm at .023" on the balance shaft and .027" on the oil pump. factory tolerances are .008"-.016" so i'm about .007-.011" too loose. so it looks like i'm ordering shims. but before so i'm going to have my buddy double check my numbers.

when it comes to the piston/rings/cylinder all that was replaced with the "niche" kit. all the rings were gapped correctly and fit tight. I do not have a bore gauge to check the small end of the rod and compare it to the wrist pin but just by feel it fits tight. I was surprised with the quality for the price of the kit to be honest

the old cylinder looked surprisingly good for having 8XX hours on it. still had visible cross hatching, with minimal scuffs on the piston but NO marks in the cylinder. the rings were within tolerance and the wrist pin was tight.

the original owners who i purchased the ranger from is actually my dentist and long time family friend. and her and her husband took the ranger to the dealer for EVERYTHING. even oil changes it went to polaris.

also, one way valve and spring is ordered

Last edited by coolcrushicekilluh; 06-24-2019 at 12:24 PM.
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post #9 of 15 (permalink) Old 06-24-2019, 02:23 PM
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The 500 engines are for the most part pretty bulletproof but they are also by nature pretty noisy too lol.
Hopefully its just a matter of tightening up the endplay a little and you'll be good to go.
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post #10 of 15 (permalink) Old 06-24-2019, 03:00 PM Thread Starter
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@polman500
im praying!
but let me ask you this.
the noise in my original post is the EXACT same noise the engine was making before the rebuild.
correct me if im wrong, but end play doesn't just happen. could end play be to blame for the original noise too?
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