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I used 4 X PTO mounts last season as well and I noticed no additional vibrations. I’ve only put 750 miles on since installing them and they look perfect.


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Discussion Starter #62
Does anyone remember the Polaris Fusions if so , one of the fixes for the tremendous vibration that these sleds had was to remove one of the grips and fill the handlebar full of bb's , I know it sounds gimmicky but I have done this many times on Polaris sleds & Arctic Cats also it actually works pretty well and is virtually free , I have 2 2020 Indy xc's and when I replace the motor mounts with 4 of the PTO side mounts I will be doing this to both of them.
Don't waste your time with the BB's. Just get the Isovibe kit from Grip and Rip. I've used this for years, works amazing.

https://www.gripnripracing.com/index.php?id_product=67&controller=product
 

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This was the thread I couldn't find a couple weeks back, I was looking in the wrong forum!

Great info guys, I will link this to my thread in the Switchback forum.
 

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So, not really interested in a vibration review, I need new mounts. As of now, I’m thinking of going back to full stock.
 

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I question replacing mounts every time you see some slop in them.

Polaris builds a lot of forward twist into the 800 setup. Way more than enough to allow the engine to self-align under load. This is apparently also to allow for wear.

I advise checking your alignment with the factory alignment tool. Then attach a ratchet strap around both clutches and tighten it as much as you can with the tool still installed. If it still indicates adequate alignment, leave it alone.

Adequate alignment is indicated when the tool is actually showing up to a .060" gap at the front and contact at the rear (Just the opposite of what the tool allows under no load).

Make sure to float secondary about .090-.120" outward from that point.
 

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When I did mine on my 18 assault 800 I did inner and outer. They seem to be holding up better than the first set. So the new part number being put into old inner mounts may have something to do with guys going through multiple sets :dunno:.
 

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Discussion Starter #68
Hey Len
You’ve really found that the 800 has enough vibration to warrant this for trail riding or are you doing a lot of hard jumping/landing etc. I’ve never found the vibration to be much myself, but I only ride trails.


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I'm 56...started using these around age 50. As you get older you start to notice the little things that cause fatigue at the end of the day. Vibration is one of them. I don't jump the sled...it's all about comfort. The Isovibe's work great. Even use them on my motorcycle.
 

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Later today or tomorrow, I expect to develop a measuring tool based off my factory alignment bar. It will quickly show you what your real c-c is. And, how much the engine moves backwards under ratchet strap load.

I'll have pics to explain it.:bc:
 

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I'm 56...started using these around age 50. As you get older you start to notice the little things that cause fatigue at the end of the day. Vibration is one of them. I don't jump the sled...it's all about comfort. The Isovibe's work great. Even use them on my motorcycle.
I noticed the vibrations starting to get to my nerves (lol!) with my 2011 SBA. Got much better after swapping in wossner pistons though.
Fast forward to 2016 and my 2015 600 Pro-X SB.
Handlebars were buzzing so that my hands got cold constantly , and sometimes numb too. Very uncomfortable!
Bought a Doo 1200 as a backup/loaner which ended up as my main ride in '17 and 18.

I guess I shoulda ordered a couple sets of those isovibes to keep my hands in good shape. And I'm not 50. Yet.
 
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Later today or tomorrow, I expect to develop a measuring tool based off my factory alignment bar. It will quickly show you what your real c-c is. And, how much the engine moves backwards under ratchet strap load.

I'll have pics to explain it.:bc:
Put my 2019 XC 850 in shop Friday. Raised it up, removed belt, installed my alignment bar today

Much to my surprise, the original forward engine twist seems to be a bit less. Almost two years or so ago, I measured about a .028" gap at front of the secondary and about .050+" at back. C-C measured 10.706". .081" too much.

I now have about .010-.015" in front and maybe .020-.025 at rear. I'll measure this with feeler gauges to get an exact number tomorrow.

I then measured exactly where the front of the secondary lines up with my tool and scribed a mark on the tool. I also scribed a 2nd mark on the tool where it lined up with the rear of the secondary. It measured exactly 8 5/8" between those marks. Halfway between those marks is the exact center of the secondary. I then scribed a 3rd mark on the tool on that center. I now have the location of where the center of the secondary is on my tool.

I then went to the other end of the tool to find the center of the primary. By design, it's halfway between the two small stubs that locate the tool.
I scribed a 4th mark on the tool at that location.
Measuring towards the rear 10.625", I scribed a 5th mark on the tool. The difference between that mark and the 3rd one is the amount of forward twist/excessive c-c. Mine appears to be about .030-.040". I will now double check what the exact measurement is by removing the secondary and determining just how accurate that measurement really is.

Then, I'll then reinstall the secondary and install a ratchet strap and see how far the engine twists backward under simulated load.

Info and Pics to follow tomorrow..
 

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This is great stuff. So, if you see your mounts with the fingers all wore off and the mount looks like a round rubber circle, they still may be OK.
 

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This is great stuff. So, if you see your mounts with the fingers all wore off and the mount looks like a round rubber circle, they still may be OK.
Probably not.

If your mounts are wearing as fast as you claim, better check clutch balance. I had mine balanced on my 2015. It was 3.5 grams out. My 2015 mounts are still in excellent condition at 4600 miles. And, I run the BMP stage I setup at about 170 hp.

One other thing to consider is engine rpm most used. There will be a critical harmonic at a particular rpm. This will cause lots of wear to many things. On a Yamaha twin tested at DTR in 1989 (Vol #1, #4). it was 7800 rpms. The carbs would begin to foam the fuel and seize the pistons. In one case, the clutch would wear out in 100 miles.

I believe folks are making a mistake in using too hard motor mounts, as this makes it worse.

The 2020 Polaris 850 has been experiencing a bad problem with coolant temp sensor wiring vibrating the connection and losing contact.
Coincidentally, the Mag side engine mounts were also changed to tougher ones. Is this a contributing factor?
 

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Put my 2019 XC 850 in shop Friday. Raised it up, removed belt, installed my alignment bar today

Much to my surprise, the original forward engine twist seems to be a bit less. Almost two years or so ago, I measured about a .028" gap at front of the secondary and about .050+" at back. C-C measured 10.706". .081" too much.

I now have about .010-.015" in front and maybe .020-.025 at rear. I'll measure this with feeler gauges to get an exact number tomorrow.

I then measured exactly where the front of the secondary lines up with my tool and scribed a mark on the tool. I also scribed a 2nd mark on the tool where it lined up with the rear of the secondary. It measured exactly 8 5/8" between those marks. Halfway between those marks is the exact center of the secondary. I then scribed a 3rd mark on the tool on that center. I now have the location of where the center of the secondary is on my tool.

I then went to the other end of the tool to find the center of the primary. By design, it's halfway between the two small stubs that locate the tool.
I scribed a 4th mark on the tool at that location.
Measuring towards the rear 10.625", I scribed a 5th mark on the tool. The difference between that mark and the 3rd one is the amount of forward twist/excessive c-c. Mine appears to be about .030-.040". I will now double check what the exact measurement is by removing the secondary and determining just how accurate that measurement really is.

Then, I'll then reinstall the secondary and install a ratchet strap and see how far the engine twists backward under simulated load.

Info and Pics to follow tomorrow..
Spent some time Sunday rechecking my c-c and clutch alignment more precisely.

I found that my original measurements were pretty close. I have .030" gap at front of secondary when pushed all the way in and .088" at rear. This became .000 at front and .059" at rear when pulled outward to touch tool. This is barely within Polaris specs. Way too much forward engine twist.

Placing a ratchet strap around the clutches and tightening as much as possible only closed the c-c by .017".

I then removed the secondary and precisely measured c-c.at 10.711". This is .086" too much vs the spec of 10.625". The hub of the primary is 1.614", the jackshaft is .807". Adding these together and dividing by 2 gives 1.273" to their centers. The gap between them measured 9.438" plus 1.273 = 10.711".

So, in order to reduce this to a much more reasonable .020", I plan to shave .086-.020" or .066" from the left rear motor mount and shim the
Left front by the same amount.

Relocating the mount brackets as I originally planned (and recommended on Snowest) is not the correct thing to do as it isn't going to maintain the proper centerline angularity between crankshaft and jackshaft.

Here's some pics showing my alignment tool scribed lines and installed alignment.
 

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Great Info!

Please correct me where I am wrong!!

1- Polaris mounts engine with forward twist of .060 +/-
( for engine to twist/move rearward under load and achieve true alignment )

2- Alignment tool already has this .060 twist built in so...The additional gap witnessed between the rear of
tool and secondary is further engine twist.

3- if under (rachet strap) pressure the engine motor mounts can only be forced to compress .017...then it
stands to reason that given the best case factory alignment...we still have .040+/- too much forward
engine twist....plus whatever additional gap you may have at the back of the alignment tool ?

Wouldnt it be true ( if my thinking is correct) that only paying attention to and correcting C to C by moving only the PTO side of the engine rearward could actually create misalignment in the opposite direction?
Perhaps too much rearward movement only?

Shouldn't parallelism take precedence over C to C in this case?

It seems obvious that any mis-alignment of the clutch's is a recipie for heat and inefficiency.

It appears that improved alignment should be fairly easy to achieve if we only need to address two locations....I am hoping !


Thanks for taking the time and effort in documenting this process for the rest of us!!
 

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Parallelism will definitely be maintained at no more than .020" twisted forward. Not .086" as now.
This should create near perfect alignment under launch load. See my other 850 breakin thread for more detail.
 
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