Stripped rear shock mount

[jave101]

Hey guys,
Got myself a 1980s GS400e and I want to have a crack at doing a cafe racer. At the moment I'm just trying to get the thing running right, previous owner managed to screw things up a bit.

So after taking the rear shock off I found the threads on the upper shock mount were chewed to pieces.
Any ideas apart from removing and re manufacturing a new mount?

Thanks James.

[jave101]

Thanks for doing that.
Nah the threads were left in the dome nut, you can see 2 threads or so still intact as the nut must have bottomed out.
I really don't want to have to cut the whole mount out, but looks like I might have to. It's welded in on both sides of the frame gusset.

[salty_monk]

The nut does not really see any force & is quite often overtightened it seems.

I think you'd be fine filling it round & running a next size smaller die down it...

You could also cut it flush with the frame, drill & use a shoulder bolt of the right size too as you have easy enough access to the rear to hold the head.

[chuck hahn]

Get a threaded bolt the same thread as the nut thats long enough to go from the INSIDE of the frame to the end of the existing threads. Next, measure the diameter of the new bolts UNTHREADED SHANK part.

Now, cut the goobered threads off but leave the bigger part the shock rides on. Drill straight thru the entire remaining stud the diameter of the new bolt. Next, cut the head off the new bolt and insert it into the hole you have drilled thru the mount and flush it up with the inside of the frame. Now plug weld the new bolt to the frame and grind any weld you need to to make it look decent and not hit the tire. You basically have made a sleeve from the old mount that will now accept the new "CORE" bolt. Repaint the frame. Follow me ??

EDIT...You want to leave the bigger part the shock rides on because it is already structurally welded to the frame and the new "core bolt" will just help add a little inner stiffness....it will be every bit as strong as if the problem had never happened. And a hardened bolt will be all that much stronger still!!! Go at least a grade 8 hardness

[mrbill5491]

The nut does not really see any force & is quite often overtightened it seems.

I think you'd be fine filling it round & running a next size smaller die down it...

You could also cut it flush with the frame, drill & use a shoulder bolt of the right size too as you have easy enough access to the rear to hold the head.

Both of my rear shock top mounts are like that. I did the next smaller die down and its been like that for years now. Though I'm sure I'm going to have to replace them at some point.

[mrbill5491]

Get a threaded bolt the same thread as the nut thats long enough to go from the INSIDE of the frame to the end of the existing threads. Next, measure the diameter of the new bolts UNTHREADED SHANK part.

Now, cut the goobered threads off but leave the bigger part the shock rides on. Drill straight thru the entire remaining stud the diameter of the new bolt. Next, cut the head off the new bolt and insert it into the hole you have drilled thru the mount and flush it up with the inside of the frame. Now plug weld the new bolt to the frame and grind any weld you need to to make it look decent and not hit the tire. You basically have made a sleeve from the old mount that will now accept the new "CORE" bolt. Repaint the frame. Follow me ??

EDIT...You want to leave the bigger part the shock rides on because it is already structurally welded to the frame and the new "core bolt" will just help add a little inner stiffness....it will be every bit as strong as if the problem had never happened. And a hardened bolt will be all that much stronger still!!! Go at least a grade 8 hardness

Interesting fix. I would like to see pics of it. I'm a visual type person lol.

[daturat100r]

Just repaired one of my gs's mounts a couple of weeks ago ,just ran a 3/8 unf die down existing and fitted a nut.took bout 2 mins all done

[barnbiketom]

Just repaired one of my gs's mounts a couple of weeks ago ,just ran a 3/8 unf die down existing and fitted a nut.took bout 2 mins all done

+1

TWO minutes why not bee happy?

[jave101]

I just ran a die down through it, got enough of the threads back to be able to torque the nut up.

All good thanks for the input

[chuck hahn]

I havent done it on a bike. But the mounts that hydraulic cylinder eyes slide over are basically the same in kind and broke threads or things happen and the fix I described is what ive used to repair the machines. Most people with real life mechanical skills transfer from machine to machine because...well, a motorcycle is just ANOTHER form of a machine..nothing special or tricky about any of it really.

[sedelen]

You're lucky, I had one in which the treaded stud was completely sheared off, had a new threaded part welded on.
As for yours, I'd just go the next size smaller. Can't see where it would hurt anything as the shock rides on the smooth area of the stud.

[1_v8_merc]

Retap next size down, get a nut to match.

[chuck hahn]

Actually that would be run a DIE the next size down on it...taps thread holes.

[wottenad]

Here's my story: when I started to remove the acorn nut on the left side shock of my 79 GS1000L, it was really spongy and I knew what that meant: when the nut came off, most of the threads on the shaft came of with it! The worst of the damage was about 10mm in (almost 1/2 way to the solid shoulder), with a 3-4mm section about shredded down to about .340" - no thread at all on the shaft and the rest of it was the stock 10x1.25 threads flattened completely.

After looking at every thread that covered this scenario and weighing the options, I took the path of least resistance and tried re-threading the remaining stud with a 3/8-16 die and it worked (really spectacularly well I might add)!

I don't know if I screwed up by not grinding the shaft down, but using a 3/8-16 die and cutting oil, I very gingerly started turning it down the shaft and it was surprisingly easy to cut the new threads into the old messed up shaft and threads! After 10 minutes I was done and the new stainless acorn nut I grabbed from the hardware store spun right on with no issues! The new threads aren't super clean, but they look like they will do the job just fine.

Since it only needs to hold the sissy bar and the shock to the shaft, it's not going to take a lot of torque, so I think with a little Loctite blue on assembly, there won't be any issues. The bike's in superb shape and I've owned it since 1985, so if this is the worst thing I'm faced with getting this 37 year old machine back on the road, I'm a happy guy!

Walt