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Sheared Motor Mount bolts

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Old 07-31-2014, 05:31 PM
johnod
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Default Sheared Motor Mount bolts

I recently got a 97 FLHTCUI , as I've mentioned before.
One of the things the previous owner mentioned was motor mount bolts shearing under hard use.
The 2 front bolts from case to mount.
Well this has now happened to me, one was gone , and the other sheared at the top of the nut.
The small piece of bolt left was grade eight, so I assume both were, I have NOT been hard on the bike, very easy in fact, usually shifting at not more than 4000 rpm.
Today I replaced them with grade 9 bolts, flat washers on both sides and nylock nuts.
Any one else experience this and found what the problem is?
I read the thread below as well, found some suggestions but not the answer.
Also can someone tell me what the clinometer test is, can I do it at home?


Thanks for any input.




https://www.hdforums.com/forum/evo-c...unt-bolts.html
 
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Old 07-31-2014, 06:12 PM
Old-Evo
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Yeah, that's my thread from last year. So far the best I've been able to do is use 1 3/4" grade 5 bolts with locktite and a nylon nut tightened down as tight as I can. I have only lost 1 this year, but then I haven't put on as many miles as I did last year. If you get it figured out please let me know, as none of the shops around here have ever heard of this happening so often. I can always tell when it goes because my left floorboards start to vibrate, then I have to find my spare and fix it on the side of the road.
 
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Old 07-31-2014, 09:38 PM
johnod
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Originally Posted by Old-Evo View Post
Yeah, that's my thread from last year. So far the best I've been able to do is use 1 3/4" grade 5 bolts with locktite and a nylon nut tightened down as tight as I can. I have only lost 1 this year, but then I haven't put on as many miles as I did last year. If you get it figured out please let me know, as none of the shops around here have ever heard of this happening so often. I can always tell when it goes because my left floorboards start to vibrate, then I have to find my spare and fix it on the side of the road.


I was hoping you'd chime in on this and say it was simple fix, like the gas cap was too loose .
O well..


Did you mean 3/8 grade 5 bolts and not 3/4?
Did you have a clinometer test done? ( I have no idea what that is)
 
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Old 08-01-2014, 03:04 PM
Old-Evo
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Originally Posted by johnod View Post
Did you mean 3/8 grade 5 bolts and not 3/4?
Did you have a clinometer test done? ( I have no idea what that is)
The bolt is 1 & 3/4" long. It's a 3/8, 16 course thread, grade 5 bolt.
I went with a softer bolt in the hopes that it will give abit more and not shear so quickly like the grade 8.
The other thing I did was grind away at the threads in the middle of the bolt at the shear point in the hopes it will last longer

Let me know how the grade 9 works.

No clinometer test done.

The closest thing I've gotten to an answer was from an Indy shop. He told me to put a wedge in-between to try and prevent the bolt from shearing off like it does so often.

For me it has always been the left bolt that has sheared. The right bolt that is hidden under the oil filter has loosened up but never sheared off, thank God.
 

Last edited by Old-Evo; 08-01-2014 at 03:30 PM.
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Old 08-01-2014, 06:25 PM
machinehed
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According to the manual , Harley uses all high grade bolts etc.
Your shearing of motor mount bolts suggests that your drive train is not true .
There is a procedure to follow in Harleys manual to true your drivetrain .
If you are breaking motormount bolts , there must be reason ...?
My suggestion ... if you dont have a Harley manual for your bike , get one now.
You have described a very serious problem that is not common and could result in expensive motor repairs if left unattended.
Come back when you are ready .
 
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Old 08-01-2014, 06:59 PM
Old-Evo
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Originally Posted by machinehed View Post
According to the manual , Harley uses all high grade bolts etc.
Your shearing of motor mount bolts suggests that your drive train is not true .
There is a procedure to follow in Harleys manual to true your drivetrain .
If you are breaking motormount bolts , there must be reason ...?
My suggestion ... if you dont have a Harley manual for your bike , get one now.
You have described a very serious problem that is not common and could result in expensive motor repairs if left unattended.
Come back when you are ready .
I did fail to mention that I addressed this very same issue with my Indy shop. He checked and aligned the drivetrain and also checked all the other motor mounts.
 
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Old 08-02-2014, 09:34 AM
4_stroke
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It may be sacrilege but you could use metric socket head bolts M10 thread. They are slightly larger in diameter but fit the holes. They are grade 12.9 as well. That would be bullet proof!
 
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Old 08-02-2014, 07:16 PM
Old-Evo
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Originally Posted by 4_stroke View Post
It may be sacrilege but you could use metric socket head bolts M10 thread. They are slightly larger in diameter but fit the holes. They are grade 12.9 as well. That would be bullet proof!
I will find one of these and give it a try. Thanks
 
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Old 08-02-2014, 11:07 PM
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4stroke, thanks for that idea.


I may have to look into those
 
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Old 08-02-2014, 11:08 PM
johnod
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Originally Posted by Old-Evo View Post
I did fail to mention that I addressed this very same issue with my Indy shop. He checked and aligned the drivetrain and also checked all the other motor mounts.


Was anything out of whack?
Make any difference?
 
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