​​​​@Max Headflow can you elaborate, I'm not sure I understand.

 

Isn't a new thing, played this game in the early 80's with a set of mags for the shovel. Finally drilled and safety wired them, only way I could get the bolts to stay put on that rear and this was before before any real horsepower came into it.

 

OK.. There are a couple issues that can occur.. The mating surface not being flat. If the surfaces that are being clamped and clean and the pulley moves at all, the surfaces can grind into each other and the bolt loses tension.

The issue to worry about with this setup is similar. Look at the picture below. There are 3 7/16-14 bolts standing on end that could be used for pulleys. Left to tight, Socket head cap screw, stock HD bolt, ARP bolt. Look flat surface provided by each, They measure 0.600", 0.560", 0.750" respectively. The center stock bolt has only 0.560" OD of clamping area. It actually works OK if it sits on a thick hardened washer. So place it on a piece of non hardened steel and the steel can squash out just like stepping on a dog turd. Maybe not as dramatic but enough to loose tension on the pulley mating surfaces. As soon as that happens the pulley moves, rattles on the bolts and the bolts snap off..

 

I wonder if using heavy conical compression washers like used in stamping die applications may be helpful in this situation ? I've seriously considered doing this on my 17 RK as a preemptive sort of deal.

 

The bolts got so far out, they hit swing arm. By being out that far, that is no longer shear load breaking them. They were bending from the lever action .

What's interesting is that locking plate is actually two plates. The first one goes on as a washer.

The bolts are torqued down and tweaked so that all line up properly to accept the next plate which has a 12 point hex
broached in it.

Then obliviously, I guess three holes were drilled and tapped in the OEM wheel.

No way a stock Harley has the power to shear off 5 bolts unless they backed out. If that was possible, all our pulley would be shearing off .

How they backed out all the way to the swing arm is the mystery to me unless the outer locking plate came off first . Pretty obvious there was no locking compound on them.

Also note the bolt if they supplied them are grade five 3 dashes.

I have only changed out two pulley sprockets. A Sporty and a Softail. They were 6 dash grade 8 bolts. Both was still factory installed. My 3/4 impact beat a few times before bringing them out.

Did the rotors too. There toric. I dare say, there so locked up, without heat, or an impact, the toric head would go before they come out.

Done correctly, those bolts don't come out on a stock Harley. Now take that with a grain of salt. Some people drive like a Nascar driver on the final few laps.

That will break most anything. Why Harley had to go to the cush drive on the drive pulley just to get their bikes to last thru warranty.

 

Some of the younger guys will probably be scratching their heads ... Safety wire? ... Any good collection of tools would include a spool of safety wire ( usually stainless ) and a decent pair of safety wire pliers ... Of course you had to know which way to "thread" the safety wire too

 

Looking at the OP's pic, reading @Max Headflow explanation and adding my albeit limited previous knowledge, those bolts didn't shear from hitting the swing arm, they sheared at the mating point of the pulley and the wheel. I'm sure they did come into contact with the swingarm and obviously caused the lockup but just looking at the remaining length you can see that they broke on the inner side of the pulley, not the outside. Also, there is no way you could clean break all 5 at the same length from hitting the swingarm. Saying all that doesn't help the OP but I'm trying to have the best understanding of this as possible.

@Max Headflow correct me if I'm wrong, but with the lock plate there is a limit to how far the bolts could back out, right? I mean clearly, they lost enough tension to shear, but it's not like they're going to back out far enough to hit the swing arm, that would be impossible since they can't each make a full rotation while captive in the lock plate? I'm interested in this and posted in the thread I linked because I have a similar setup on my chain drive.

 

Not sure what you are saying above.. The bolts did not back out. The bolts lost compression, pulley came loose enough to rotate then the bolts sheared at the end of the thread inside the wheel where they were unsupported. The remaining parts of the studs in the hub are likely to still be loctited in place, at least a couple of them.

 

That's exactly what I was saying.

 

so in over all what do you think happened? Maybe it was the plate that caused just enough for bolts not to sit tight enough ? I don’t know the damages yet as it’s long weekend and they prob won’t get on my bike until next week. I talked to other guys who actually have stupid motor work done to their fxdx with no issues not running a plate lock either. Just proper bolts and torques to specs. But at the same time they have all heard of this happening. My one friend went through this 3 times. Each time doing a differnt method to stop this. Between the wire method , plate method and multiple manufacturers of the plate. The only thing right now for peace of mind I can think of is to mark them so I have a visual if the bolts moved and check them every time before I ride. If they do come loose during a ride they would have to get loose enough from being at torqued specs and back out and I think and hope luck and time would be on my side to be able to see the bolts came loose. Only reason why I prob didn’t even notice this as well is because I had bags on bike that cover this area. And it also wasn’t something I’m looking at but going forward I know I will be but it’s not a good feeling in the back of your head riding.