Primary clutch bolt broke off today....
- Thread starter 94fordguy
- Start date
Correct. The reason these bolts break is due to the increased torque spec Polaris put out in 06. The original bolt was "Designed" for 50 ft. lbs? I will continue to follow Polaris' torque spec on this one AND continue replacing the bolt AND washer at the beginning of EACH season.
The main reason I will continue at this spec is ALWAYS after I replace a bolt and torque to 96 ft. lbs. EVERY pre-ride check for the first 3 rides afterwards, I will find the bolt takes just a little more torque each time. Generally after 3-4 checks, the bolt will finally be holding 96 ft. lbs. and will continue holding until the clutch is removed the next time.
A $21.00 bolt and washer each season and the investment of a torque wrench to make this check part of your pre-ride inspection is certainly alot cheaper and safer than a broken crank. In this case, blaming the spec rather than replacing the bolt each season could lead to trouble.
Remember how much of a shaker the 900 is. Remember the heat of your clutch after 60-90 second full pull in the deep. This is where eyes open when an infrared temp gun is used. This clutch needs all the retention it can get. Would Seths' clutch had stayed on the crank without a bolt if it had only been torqued to 80 ft. lbs.?
Aren't you stress hardening the bolt by doing this, and therefore making it more brittle and more susceptible to a fatigue failure?
I think the 96 ft pds is for the initial pressing on of the clutch and really doesn't need to be that tight afterwards. I remember in a old post from indydan to tighten the primary bolt to something like 96 ft pds and then back it off and retorque it to 80 ft pds or something like that on the 800's the way I look at it be glad it was the bolt and not the clutch braking like I have seen in posts on here. thats the one that scares me
Yes. But the vibes and the heat placed on the taper of the crankshaft will allow the bolt to back out at a lower torque spec which is why Polaris increased the torque spec in the first place. I've seen 2 of these break with my own eyes when set at lower than Polaris rec'd settings.
It's up to you guys what you want to doo. A new bolt and washer each season and routine pre-ride torque spec checks (with a quality torque wrench, Snap-on is the ONLY torque wrench i would use BTW) like I've already indicated that works without issues
OR
Take your chance reusing a bolt that's already over it's design spec at 80 ft. lbs saving your $20 and run the risk of breaking your crank when the heat of the clutch and the vibes of the motor cause the bolt to loosen and or break and break your CRANK.
We just saw pics of what I believe is NOT replacing your bolt each season. Very very very lucky this didn't end in catastrophe.
As far as torquing to 96 ft lbs and then loosening and retorquing to 80 ft lbs...this would be a no-no on a tapered crank. This would be like loosening a crush sleeve in a differential. The decrease in preload could allow the clutch to lossen back to the 80 ft lb, thus causing the bolt to losen up. If you only want to run 80, then only go to 80.
Actually, The bolt was new at the beginning of the season... 930 miles is all this bolt could take at the recommended 96 ft-lbs... Maybe it was just a bad bolt, IDK...
I will agree with one question you ask... Would the clutch have stayed on the crank with the bolt only torqued to 80 Ft-lbs?.... I surely don't know, but I am grateful that it stayed on for me.
I will agree with one question you ask... Would the clutch have stayed on the crank with the bolt only torqued to 80 Ft-lbs?.... I surely don't know, but I am grateful that it stayed on for me.
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Actually, The bolt was new at the beginning of the season... 930 miles is all this bolt could take at the recommended 96 ft-lbs... Maybe it was just a bad bolt, IDK...
I will agree with one question you ask... Would the clutch have stayed on the crank with the bolt only torqued to 80 Ft-lbs?.... I surely don't know, but I am grateful that it stayed on for me.
I apoligize. I didn't read where it had been replaced earlier this year. I remember a couple years ago guys questioning of this increase in torque and wondering if the bolt should be replaced with each clutch removal? Had you removed your clutch any during that time? How about a pic of the washer, maybe sitiing next to a new one.
Certianly this isn't an everyday occurance, don't see it that often. However, we are taking the bolt beyond it's actual design strength so installation with an ACCURATE torque wrench becomes very important. If we install this bolt that's already being torqued beyond it's design, then accuracy becomes even more important. I'm a torque wrench addict. Mine are sent in every year for calibration. I'm not saying that you guys should doo this however, I stress a quality torque wrench and unfortunately the only one I've ever found to be accurate is Snap-On.
I love comparing my co-workers cheaper tw's to mine. I've found many to be off a fresh calibration to ine by 25% and more.
This bolt could've broke for more reasons than we've discussed. I would be curious to see if the clutch galled or slipped on the crank during the ride out.
Another note...I've been finding the washing getting very galled and chewed up from the head of the bolt. With this and it being tapered/concaved, it would be a good idea to replace this along with the bolt.
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The clutch had been removed one time by me immediately after I bought the sled last summer (the whole motor was rebuilt immediately prior to my purchase of the sled) in order to install my SLP vent kit. The bolt had obviously not been torqued to the 96 ft lb spec as it came loose very easily as did the clutch, I suspect the bolt was most likely torqued to the old 50 lb spec. After giving the clutch a quick cleaning I put it back on at the 96 ft lb recommendation and re-checked the torque several more times to ensure it had not backed off.
Yes, both the brass washer and the other washer/bushing are both noticeably concaved from the torque stress and I ordered a new set of each of them along with the new bolt... I didn't want to risk putting anything used back on there.
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I've been running a 98 Poo 700 motor for the last 7 years with a broken clutch bolt...just never got around to pulling the threads out and it's held on just fine. Should try running my 900 the same way and just maybe the clutch would finally work it's way off...
I find it hard to believe that Polaris would put in a bolt that cannot take the recommended torque. Where did you get the information it was beyond the bolt's design strength?
I don't know the diameter of the bolt where it necks down or the grade of the bolt, but the general reference says a 1/2 bolt grade 5 has a torque rate of 75 or 90 lbs depending on the thread count. A grade 8 bolt is 110 and 120 lbs. Seems inline to me.
I'm just thinking that if the bolt is understrength then Polaris should be on the hook for any damages that occur if the bolt breaks irregardless if the bolt is replaced or not after every removal. That is why I wanted to know where the information came from regarding the bolt is overstressed. Is it only a grade 5 bolt for sure? I looked at mine on a 2010 RMK600 and it has 10.9 SP? stamped on the head which as far as I can find out puts it at a grade 8 equivalent and it should be made of alloy steel. Recommended torque is 80 ft lbs. for it. This is a good thread.
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