Oil Filter Stud thread repair

[tobaccorancher]

I am in the middle of repairing the threads in the crankcase for the lower right oil filter stud.

I just drained the oil to work on the clutch and noticed that the fastener was different in that location than the other two.

It seems that a PO had trouble with that stud and drilled and tapped it for 1/4-32. The fastener in that location was a 1/4-32 bolt with a lot of washers as spacers.

My original plan was to install a 6X1mm helicoil. The drill size for that is 1/4 inch. I removed the exhaust, made jig so that I was sure that I was drilling straight and drilled it out to 1/4 this afternoon. I used a new bit and used grease to help get a nice new cut. It seemed like the drilling process was a bit too easy. After drilling, I still see a faint outline of the threads that the PO cut.

So, I am at a crossroads. I think that I could continue with the helicoil install and be ok, I think the tap it much larger than the remains of the damaged threads. But, I want to make sure that I am not making a huge mistake before I continue.

I looked at switching to Time Sert, but the drill for that is a size D drill bit (0.246 inches). I have already drilled to 1/4.

The next step up would be the Big Sert. The drill for that is an L bit, 0.290 inches. It looks like that drill size would take me into the o-ring.

So, I think that the only options at this point are to continue with the helicoil or Time Sert. For the helicoil option I am considering installing the helicoil with red loctite to strengthen the helicoil engagement. Or, maybe I am over-thinking of this. Can I get some opinions of some of you that are machinists or have done a lot of thread repairs?

Thanks,
Andy

 

[bwringer]

What IS it with previous owners, their obsession with hack repairs, and their utter unfamiliarity with the metric system?

"There is no curse in Elvish, Entish, or the tongues of Men bad enough for such treachery."
Treebeard, J.R.R. Tolkien, The Two Towers


Not a machinist, but have done lots and lots of GS thread repairs.

I'd go right ahead with the helicoil. For one, tapping will go past that faint outline. For another, there is just very, very little stress on these threads.

And I'm sure you're already doing this, but go ahead and replace all three of the studs while you're in the mood. Heat them up some, then clamp on and wiggle with vice-grips until they start to move.

Also, for anyone else (which is every GS owner at some point) dealing with this, another option is to get a stud with an 8x1.25mm thread on one end and the 6x1.00mm thread on the other. These are called "stepped" or "step down" studs. Drill and tap the case to 8x1.25 and you're good.

Something like this; I'm not sure these are the right length:
https://belmetric.com/m6-to-m8-stepp...ss-8-8-steel/?

Finally, the other studs that strip out on every GS at some point are the 8mm studs at the bottom of most GS forks (not on the leading axle "L" forks). I keep some of these on hand. Apparently, people are terrified that the wheel will just fall off, so these always get badly overtorqued, plus they're made of soft cheddar cheese like the oil filter cover studs.

 

[bitzz]

E-Z LOK thread insert
M6x1.0 ID
Drill 8.6mm (0.339") and tap to M10x1.5
They come in two lengths

or you could drill it out and install a plug.... I would probably weld it up and drill and tap a new hole

 

[tobaccorancher]

Thanks, guys. I have all three new studs, so will be replacing them all. Are they installed with thread locker? Also, I am assuming that the short end gets screwed into the crank case until it bottoms out at the middle shank. Sounds like there are methods for a lot more damage than mine had, so I guess mine are not in as bad shape as I thought.

 

[bwringer]

Thanks, guys. I have all three new studs, so will be replacing them all. Are they installed with thread locker? Also, I am assuming that the short end gets screwed into the crank case until it bottoms out at the middle shank. Sounds like there are methods for a lot more damage than mine had, so I guess mine are not in as bad shape as I thought.

Yes, that's all correct. Short end in, and blue thread locker would be perfectly sufficient. You just need to keep the studs from unscrewing when you change the oil. There's no need for red here.

FWIW, I use nyloc nuts here, and replace them every few oil changes. That way, I know they won't unscrew themselves and I can use only enough torque to compress the o-ring. I keep OEM o-rings on hand, and the GS gets a fresh one every few years. One o-ring will easily make it through several oil changes.

 

[tobaccorancher]

OK, I got the two remaining studs out without much difficulty by double-nutting them. They were 6mmx1 all-thread, and were too long. The threads looked ok with a flashlight, but I am having difficulty threading the correct studs in by hand. I can get started in what seems like a good thread and then it gets stiff. All that I have used so far on them is the double nut and my fingers. I am thinking that I should be able to thread them in by hand. I tried one of the studs that I had removed and I can get it to thread into one hole, but not the other. So, I am thinking that the threads need to be chased with a tap? After all the pain for this I don't want to go backward. Thanks! Andy

 

[bwringer]

Yes, there's probably crusty old thread locker down in there.

Chase the threads (gently!) with a tap, flushing frequently with WD-40 or whatever. Getting a tap handle to work down in there will be difficult or impossible, so you'll need a tap socket or some other way to turn it, and/or supreme patience.

 

[tobaccorancher]

I have a couple T-handle tap wrenches, I think my small one will be the right size, is that what you mean?

 

[bwringer]

What I meant was that it's probably too deeply recessed to get a full swing with the tap handle. You can slide the tap handle one direction, then the other to slowly make progress.


Tap sockets are kind of a specialized thing, but they are very useful for driving taps with a ratchet and extension.

 

[tobaccorancher]

I have my exhaust off, so have plenty of room, no problem fitting the tap wrench in there, unless I am missing something. I can't seem to find a 6mm tap, so this won't be happening today anyway, though

 

[tobaccorancher]

OK, got back into this today. I was pretty careful chasing the threads; I made a jig to make sure that my initial angle was good, and I used cutting oil on the tap. I got a surprising amount of swarf when I chased the threads of the two "good" stud holes. I rinsed the holes out with seafoam and "unscrewed" the debris with Q-tips, it took a lot of Q-tips to clear all of the debris, but they look good now. I think that they had been over-torqued, but perhaps not as bad as the lower one. I also tapped the lower hole in preparation for helicoil, so am ready to install the helicoil and studs.

I think that the threads for the two upper studs are a bit weakened by the previous over-torquing so I intend to use thread locker when I install the studs. bwringer recommended blue earlier, would that still be the recommendation? Also, for prep for helicoil and stud install, should I flush the threads with acetone or alcohol to clean the oil from the threads before installing the helicoil and studs?

I realize that I am probably over-thinking this, but that is what I do.

Andy