I think I read an earlier thread about how the bolts supplied by HB with their bars were cr*p. Today I found my lower right bolt sheared off and I suspect the vibration from the bars took its toll on the crummy bolt (bike has never been laid down).
Care was used in installing and correctly torquing the bolts.
I plan to replace both HB engine mount bolts with #8 grade ones asap.

Ted,

Did you have any problems tightening the nuts (the ones that SHOULD be 'captured' in the cases) when you first buttoned everything up? If so, what did you do to hold them?

Ed :cheers:

Ed
No problems with the nuts being tightened in the cases AFTER I took the bolts and nuts and tightened them at my workbench (before attempting to mount them in the bike). The nut and bolt threads had to be "worried" together - tightened a little, backed out, tightened a little farther, etc. The replacement one I put in yesterday needed the same thing done to it. Is that what you meant?
Learned something about bolts: I was looking for a grade 8 replacement but could only find grade 8.8 metric at the hardward dept. I was told that 8.8 is "better than grade 8". This is not so, it's like grade 5. So am still on the lookout for a 10 mm grade 8.
The bolt that came with the crashbars was much softer than the stock nut that I used. It sheared cleanly - just like it had been cut. Of course when it broke the spacer between the frame and motor mount was lost. So in addition to finding a grade 8 bolt, the replacement spacer will be wired in (somehow). Don't want to loose another spacer, but also really don't want that spacer dropping off my bike in traffic. Yikes to anyone behind me with that small iron piece flying about!
Ted

Ed
No problems with the nuts being tightened in the cases AFTER I took the bolts and nuts and tightened them at my workbench (before attempting to mount them in the bike). The nut and bolt threads had to be "worried" together - tightened a little, backed out, tightened a little farther, etc. The replacement one I put in yesterday needed the same thing done to it.

I don't think bolt strength is your issue. This sounds like mis-matched or damaged threads to me. It's not surprising the bolt broke eventually if this much force was required to tighten.

I just installed some HB crashbars on an '09, and the stock locknuts and new HB bolts threaded by hand initially as they should, then I tightened them the rest of the way with an impact wrench.

In neither case (the HB bolts nor the replacement bolts) did they tighten by hand. I have built several muzzleloading rifles, and am used to "worrying in" threaded parts, so did not think it unusual.
In any case - the bolt sheared 1/2" ahead of the nut. The worrying process does not stress the bolt. So I conclude that the bolt was weak. After the bolt broke I had to dremel the nut to remove the bolt fragment. The bolt cut like butter, but the stock nut was tough.
The reason that I posted was: the HB bolts do seam to be crap.
The left motor mount design is ok and the HB will probably work there. But the longer right bolt, with separate spacer, is a bad deign, and a grade 8 bolt would be better.
I wired my replacement spacer to a frame member today. Hope the bolt will not break gain, but if it does I hope not to loose the spacer.
In my opinion: the right lower mount has a bad design, Kawi.

I can't comment about muzzleloaders, but I do know that these parts should mate without forcing them.

Trying to put a square peg in a round hole will never end in a positive result.

The threads were not damaged and the bolt sheared 1 inch above the nut. It did shear in a threaded section of the nut, though, at a point where the bolt would have been inside the engine mount casting.
Sounds like Ed may have had similar issues with bolt tightening as I.
Other threads have also noted that problem.
Where did you get your repacement bolts?

is it a 'crap' bolt or is the choice of bolt an integral part of the design of the engine bars.

is it part of the design so the bolt fails having absorbed some of the crash energy but not so much that you transfer the energy elsewhere say onto the frame.

I'd be very careful on changing the bolts on the engine bars unless you know better. the bolts for the H&B are hardly a big ticket item, so there must be a reason to choose the style and pattern of bolts they have, other than cost.

bolts brake from cross threading or "worrying them" usually by twisting and snapping if it sheared its a weak bolt, did you try mcmaster-carr or any places like that http://www.mcmaster.com/#socket-cap-screws/=3spuxo has just about everything and you can get it in 12.9 metric hardness

Most motorcycle shops also have a variety of bolts. Usally can get them for free if your on good terms with the shop.

Ed
No problems with the nuts being tightened in the cases AFTER I took the bolts and nuts and tightened them at my workbench (before attempting to mount them in the bike). The nut and bolt threads had to be "worried" together - tightened a little, backed out, tightened a little farther, etc. The replacement one I put in yesterday needed the same thing done to it. Is that what you meant? Ted

No. When I installed my HB bars, the nuts that were SUPPOSED to be 'captured' in the engine cases turned before I got to the correct torque specs. They're CLOSE so I haven't done much since, tho' I would like them correctly torqued. :goodluck:

After reading ALL the posts, I have an observation: Grade 2 bolts (the softest) will 'give' and / or bend before they break. Grade 8 are VERY strong in tension, but not in lateral loading, where they will 'snap'. So I BELIEVE that 'shear' bolts MAY be grade 8 with a waisted break-away part, for instance. (I was a fastener "expert" in an earlier life...!). Therefore, using a different strength fastener MIGHT be a bad idea, depending on the application. My .02$....

Ed :cheers:

One point missed, the bolt could have been SAE not metric. I've seen it on occasion, one bolt gets tossed into the wrong bin and you wind up with it. properly matched nut & bolts should have no restrictive force. Unless the nut is pinched to provide resistance, or its a nylock nut.

I'd be very surprised if you could get SAE or imperial bolts in Germany :)

In any case - am replacing the bolts with higher quality metrics from Fastenal. These bolts do two things: anchor the HB crash bars, but more importantly, anchor the frame to the engine mounts.
The left engine bolt mounts without a spacer (which is used on the right). I could envision lateral movement in the (right) 3-component system shearing a weak bolt.
The higher-rated bolts have much higher tensile and shear specs. vs "regular".