broken chaincase bolt...

[snow_dog]

A buddy just called me from up in Tomahawk, apparently the lower sprocket bolt sheared off and tore up
the cover gasket which started leaking. Thankfully they caught it right away before any more damage occured.

My question is, has anyone else had this happen? The sled is a 2000 XC600.
He's going to bring it back here for me to fix, I'm wondering how hard it'll be to remove the broken bolt.
The bolt has blue lok tite on it and is torqued to 19 ft lbs according to the service manual.

 

[docbubba]

hey!! happened to me and best bud is a polaris dealer. gasket is not leaking, chain case is likely broken. did chain break also?
common common on that sled...

 

[snow_dog]

They said the chain and gears look ok but I'm going to have a good look at them myself.
The large washer behind the bolt got caught up in the chain and shredded the gasket.
They literally caught it just as the leak started.

 

[raceinsnow]

This is a common problem on the polaris sleds.The bolt breaks because of the tunnel flexing and it pops the head of the 5/16 bolt right off.The best way to fix this is to drill it out and rethread to use a 3/8 fine thread grade 8 bolt.The broken bolt should come right out of the shaft.When the head of the bolt pops off it usually breaks the chain case.

 

[skeeter2010]

This is a common problem on the polaris sleds.The bolt breaks because of the tunnel flexing and it pops the head of the 5/16 bolt right off.The best way to fix this is to drill it out and rethread to use a 3/8 fine thread grade 8 bolt.The broken bolt should come right out of the shaft.When the head of the bolt pops off it usually breaks the chain case.

I had never heard the cause of the bolt breaking being tunnel flex. You would think the drive shaft slip though the bearing on the PTO side before it would pop the bolt head off.
Interesting never really thought of that before

 

[makintrax73]

This is an all too common problem, and if you do a little searching on the sled forums you run across it a fair amount. Not sure why Polaris never addressed it.

I read about it enough that I got really concerned about it. I torn the chaincase of my 600 xc-sp down and found that my lower sprocket bolt was loose. Not just a little, but loose to the point that the washer was spinning around (and I would add wearing away at the bolt little by little).

Honestly I'm not totally sure about the cause, but I did come across a fix that has worked for me so far. What you do is take a smaller washer and put it UNDER the stock Polaris beveled washer. What this does in my non-engineer opinion is a couple things:

1) Prevents torqueing the bolt from totally crushing down the stock beveled washer - thus it still has some "spring" to it to tack up any side loading on the sprocket; and

2) Lengthens the un-engaged part of the bolt. The reason I think that might be important is that a bolt is like a spring - a really really stiff spring, but a spring nevertheless. I think this may allow a greater area of bolt to aborb side loading of the sprocket, and thus cut down on stress concentrations. Spread the side load stress over a greater area.

I saw this 2 washer suggestion a couple of times and it seemed to work for the people who tried it. So far (knock on wood) I have not had any further problems, and I do check the bolt every season now that I know it's a problem.

_______________________________

I would also suggest being careful about centering the bevel washer on the bolt. If it does get loaded then side loads caused by an un-centered washer (and the hole in the stock washer is certainly big enough not to be centered) is going to cause side loading on the bolt - something that is going to break a bolt much faster than simple stretching. I don't know for sure that this helps, but it certainly can't hurt.

Also, clean the threads very thouroughly with break cleaner and let them dry. Install the bolt with lock tight and let that dry for 24 hours before you fill it with oil so the lock tight can dry before it can get oil in it.

 

[indy_500]

You said this is an 00 XC 600? A gen II? Never heard of this bolt breaking on a gen II before. Drill and tap the driveshaft out to 3/8" and intall a 3/8" grade 8 bolt. Make sure you reinstall with the beveled washer, and have the washer drilled out also. That is one of the biggest hassles (drilling out the washer) make sure your drill bits are sharp. Some have had better luck putting a flat washer behind the beveled. I personally, didn't seem the point in it. Make sure to put blue loctite on the bolt, and torque to 19 ft/lbs exact. I had it happen on my 05 xc 500 and did it to my other 2 sleds

 

[TW500]

It happened on my 00 500 XC SP. Destroyed the chaincase cover. Broken bolt was removed easily with a left-hand drill bit.

 

[skeeter2010]

So I have been thinking about this a little bit more so here me out.
I have a Dodge that has a NV4500 transmission they have a history of spinning off the overdrive gear. The over drive gear is held on with a retainer nut and staked to the shaft meaning pressed into a flat spot to stop the nut from backing off. This sometimes didn't work and the nut would spin off and than you would no longer have 5th gear. Nothing would be broken the nut would be on the shaft along with the gear
The cause was the helical cut gear would rock on the spline which was against the nut which was holding the gear to in the shaft. That rocking motion would loosen the nut just due to the loading and unloading.
So here is my thought, my trucks transmission would cause the nut to loosen due to the direction of the helical cut of the gear and the pressure applied to the nut.
The drive sprocket is held on by a bolt and that bolt tightens by twisting it to the right which is also the direction of rotation the drive gear. So if the gear is slightly loose on the spline in theory that gear could rock on the spline and tighten the bolt to the point of breaking the head off.

 

[rp7x]

clock wise rotation

wrong answer

 

[snow_dog]

Thanks for the replies.
I got the sled today and had a look.
It seems I wont be able to get a straight shot when drilling, even with an angle drill.
People that have done this, how did you go about drilling the broken bolt?

 

[tubbywolfe]

Remove the entire chain case and drill it out aon a workbench.

 

[skeeter2010]

wrong answer

Which would be the same direction you turn to tighten a bolt so every time you get on and off the gas it could both tighten
Just a thought, I think it is plausible
If I am wrong it isn't the first time and will not be the last

 

[rp7x]

you have to take the lower bolt out of sus. take the cowling down , the gear rotates clockwise then the bolt would loosen , don't make this fix any harder than it needs to be ,3/8" and be done

 

[bigred_tr]

Remove the entire chain case and drill it out aon a workbench.

Hate to say Tubby but the bolt would stay in the drive shaft on the sled.
Might have to pull chain case out 1st, then you will be able to move shaft at a angle.
We have a small air drill that is about 5" long that fits.It's tight but you'll get it.

BR

 

[snow_dog]

Okay thanks for the advice, much appreciated

 

[D.B. Cooper]

This is a common problem on the polaris sleds.The bolt breaks because of the tunnel flexing and it pops the head of the 5/16 bolt right off.The best way to fix this is to drill it out and rethread to use a 3/8 fine thread grade 8 bolt.The broken bolt should come right out of the shaft.When the head of the bolt pops off it usually breaks the chain case.

Correct^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

Don't know if it's tunnel flexing or that the bolt that "backs off" or was never tightened in the first place, but never-the-less it definitely IS common.

Going to the larger 3/8" diameter bolt is a good idea

Clean out the threads in the drive-shaft with brake-clean and

And use Red loctite on the bolt threads,

let the loctite dry overnight in a heated garage.

I broke the lower bolt on my 2002 EDGE-X 800 when it was only a week old, it took out the tensioner

 

[fusionfool]

hey!! happened to me and best bud is a polaris dealer. gasket is not leaking, chain case is likely broken. did chain break also?
common common on that sled...

X2 on the probability of broken case. They crack on the inside where it is hard to see. I did not find until I rebuilt with new seal, bearing, chain. Then still had leak. Ended up rebuilding with new case.

 

[snowdude]

I have never heard of this until now. I have a 02 xc500sp. I changed the track at the end of last year. Sled had 7000 miles on it then. Bolt was tight then. I lost sleep last night thinking of this since we have a big trip coming up this weekend. So I tore it apart today to have a look. Everything seemed fine. I took the bolt out (took less than 15 ft.lbs.) cleaned the internal shaft threads and installed a 1" long bolt (original was 3/4). I dont have time to do the retap idea so my thinking is an unstressed grade 8 longer bolt should at least buy me some time.

Thanks for the heads up... looks like I have a summer project now. Hopefully I dont have any problems!

 

[michaeladams]

long bit and drill through side of machine to drill out bolt. remve chain and spray it down real well. i did mine in a couple hours at runningbears. something with the perc reverse backs the bolt out and it binds on the cover and snaps off.