Socket head cap screws are typically grade 8 or better. The problem isn't the strength of the bolt but more than likely improper assembly.

First off the shock mount is typically a double ended stud.




Second, the spacer between the shock and frame like has too big of a hole in it. This allows the bolt to bend and puts undue force on the bolt. It looks as though the shock bolt was allowed to come loose and rattle.. This is real hard on hardened bolts like grade 8 so it snapped.

I'd find a competent mechanic and have him do the repair.

 

^^^
I think that's the older style Dyna shock mount. My 07 uses a hex head bolt going through the upper shock mount, through a spacer, threads into the frame/strut. bolt part number is 54718-06A

 

Same here, no double threaded on mine. Certainly change that front mount. It should not be sagging that much.

 

I'm gonna take it in and have them replace all the shock bolts, motor mounts, and do a complete front to rear service and change all fluids. Hopefully she will be ready to ride then 😊

 

Clearly the bike needs a going over by someone that knows what to look for good luck with it.

 

The picture I showed was for a 12 or 13 FXDC.. Early ones had a stud and cover.. It probably depends on which model.. My 2000 FXDX had the setup below..

Also I did switch over mainly because I wanted a SHCS up top and bottom.. They are std SS which is the equivalent of about a grade 5 (oh no!)

 

Wow

 

I went poking around some and it looks like HD only used a full length bolt in 06 and 07.. The rest of the it was a stud like shown in the pics.

 

 

I was flipping through parts manuals and noticed the same thing, bolts only used for two years 06-07.