Had been having issues starting the FXDWG with the starter button, and eventually got to where the direct start button I had installed on the solenoid did't work reliably either. So the task was to overhaul the starter solenoid, to do this the starter and solenoid have to be removed as a unit from the bike. The unit is attached with 2, 5/16” Allen screws about 2” long with an unthreaded shank of about 5/8”. One screw came off using reasonable muscle. The other was frozen in place, the more effort I put into unscrewing it the more the allen socket got screwed up. I actually broke a ball of my allen wrench and then continued with a non-ball wrench. We tried penetrating oil, impact and heating the area with a torch. This is a steel screw going into an aluminum casting on the back of the primary drive case.

We decided to drill the bolt out with a 1/4” drill and try using an EZout. The drilling went smoothly, we got the depth up to about 1/2”. Put the screw extractor in and applied some *** and bang! snapped the bolt off where the shank ends and the threads start. (Knew something was going to break off). Took the starter motor and solenoid unit off and looked at what was left of the bolt… about 1/8” of it was sticking out from the aluminum casting. So we decided, we were committed now, gotta press on with the drilling and try the EZout on the remaining part of the bolt. I put the drill on it and lightly goosed the trigger, and saw the bolt screw IN. Was able to get needle nose pliers on it and then unscrewed the whole thing, all the threads of the bolt, out with my fingers. Huh?

I asked the service manager at HD about it, then talked to a service tech with 25 yrs experience on Harleys, and then told the parts guy, a Harley lifer, and not one of them had ever experienced shearing off a bolt and then being able to remove the remainder with one’s fingers.

We have no explanation. We’re just glad that we can get on with the job tomorrow before sun up.

Other than “**** Happens and sometimes **** Doesn’t Happen” we have no explanation. Far as we can tell there was no threadlocker on the threads, no red no blue.

So there’s the puzzler, have fun with that!

 

Always use a reverse drill bit for bolt extraction. Many times it will bite and unscrew the bolt.

 

Typically release of pressure from the head of the screw being gone will free up the threads. Remember threads are friction fit and less friction = less resistance.

 

Thanks Ed, good advice... But as it turned out impossible to do, at least in our town of 7,000, we tried NAPA, AutoZone and Lowes. Really wanted to use a left hand twist drill but in order to get it in to where the problem was I needed one that was at least 8" long, cause you have to get past the unit itself to get the drill on the work. We used a 12" long 1/4" right hand twist drill to get in there.

No thoughts on how this could have sheared off and left the threaded portion finger-tight in the hole? Yes it must have been frozen in the shank portion of the bolt where it contacted the aluminum starter solenoid mounting hole. (I used anti-sieze when I remounted it.) But I don't get the physics of it all if the threaded portion ended up essentially freeto spin in the hole.

 

Well, it's not physics that caused the bolt to stick. It's chemistry. The 2 metals have different ionic properties that allow the metals to bond together when moisture gets into the joint. Water can get in easily since the starter bolts used have split lock washers. Even without the washer, moisture can get between the surfaces and into the treads. A form of electrolysis occurs and forms an oxide layer between the bolt and the hole. This layer is very tough but also very brittle. It's not hard to strip out or shear off bolts when trying to remove. I used to work in MC shops that did mostly Japanese bikes. The issue was real common but easy to get around is you knew a couple tricks.. The main one is to simply shock the bolt and crack the oxide layer. You can use a punch and tap the head of the bolt downward. A little heat can also crack that layer. Once the layer has broken the screw will come right out.. Your drilling might have created enough heat, Trying to center punch the bolt can also do it.. Depending on the amount of corrosion the screw can look clean, The layer is very thin.

 

Thanks for pitching in on this, Max. Chemistry for sure was the cause of the frozen bolt, no question at all about that. We tried heat, shock and penetrating oil and ended up with an Allen screw that wouldn't hold a wrench.

But once I freed the shank portion of the bolt with the screw extractor, it sheered off and then became a physics problem. How could it shear off and leave the threaded body of the bolt sitting there not even finger tight? In other words how could it shear off without the threaded portion being frozen too?

 

Like I said earlier, friction welded. Once the head of the bolt was gone and the stress was off of the threads they were free to move. The weak spot of that bolt just happened to be where the shank met the threads.

 

Are you saying that once head popped off the screw came free?

 

I'm saying that once the screw extractor freed the screw and sheared it off, the threaded portion of the bolt was left sitting in the threaded hole and could then be removed without tools... with my fingers only. The bolt sheared off at exactly the point where the threads begin.

 

So it was free as soon as the tension on the screw was gone.. That's typically how they come free. That corrosion holds the crew at the threads, As soon as tension is gone the threaded part pops loose and unscrews easily.