Alternate Broken Stud Fix

Hi all. So a few weeks ago I was able to pick up a "previously loved/hated" 66 HT for cheap. It was bought sight-unseen by a friend and driven an hour to its new home.

Opening up the box of parts there was cut-up rubber matting mixed in... uh oh... Sure enough, both rear studs were sheared off, and deep. One had even been drilled out and retapped to a 5/16", and that had sheared deep too.

At first I tried an easy-out, which angrily snapped off in there. Further attempts to drill a hardened stud next to soft aluminum didn't end well.

So after some thinking I came up with this:

pic1 - completed, notice the stud holes in the spacer are tapped with 5/16" for normal mounting to frame

pic2 - what was left of the studs, and my failed attempt to drill. Surface is cleaned for JB Weld

pic3 - New holes drilled and tapped for 6mx1 bolts. There's enough meat to get a good 5/16" deep into the case. The hole on the left is a little high, and ended up into the case bolt a hair. If done again keep it a little lower.

pic4 - Mod to the spacer for the longer bolts. Surface cleaned with sander for JB Weld

pic5 - Top view, used allen bolts in case. No clearance for normal heads.


Even without the JB Weld under the spacer yet it is very solid. I'd have preferred to use a solid 3/16"+ plate, but had to use what I had kicking around for now.

I'll update how it holds after the JB Weld and a couple miles on it.

More pics. Had to clearance the case on the one side. Those bits work great on aluminum(pic1).

Tip for a quick depth gauge on a drill bit, worked good.(pic2)

Thanks, both studs were still in my case too. In pic1 up top, I've threaded the holes in the spacer with a larger tap for mounting to the frame. It'll mount with a normal bracket on the back of the post. Albeit with larger bolts.

Got it on the winter bike and out for a boot today. It held up good no cracks in the JB weld. Will put it through the tow-test tomorrow to see how it fares after hauling a load of groceries/beer... to simulate a 200lb rider

btw, she screams! While it was apart I trimmed the skirt(intake side), cleaned the transfer ports(slag heaven), matched the intake/exhaust(as close as those get), intake was a mess, welds at the bend leaked insiside-cleaned that up. Pretty vibe'y at wot, but the jb weld held, so I'm thinking its just the way the engine is. May have to balance the crank in the future.

So yea, so far so good on the mount. I rode it like I stole it for a good half-hour to see if it would hold. It did.

*hear's ppl digging out old cases from junk piles*

edit- oh, btw I'm running no head gasket either, *after lapping head/jug from 220 down to 1500* no leaks there either.

Sure sure np, do you have any taps around at all? You know how to tap a drilled hole, right? If Not I can explain, or a pro will jump in while I'm typing that part. (long story short you can use a vise-grip just keep it level and keep pressure while you "turn a 1/4 to cut, turn back an 1/8 turn 1/4 to cut, etc" aluminum is more forgiving than steel) Just keep concentric(straight and centered) while you go.

Well, the bolts into the case are our standard M6x1, everything aside from the magneto cover is M6x1, (jug/head studs can be different, M6x1, M8x1, M8x1.25[1.25 is 8 threads per cm 1 is 10], so you know for future reference)

But anyways,

That's for the tap. Now for the bit, you're supposed to use a 1mm size less than the tap. I only have imperial bits around, so the closest I could find to 5mm is 13/64, I tried 3/16 but it was too tight for the tap. (Reference)

All that was for the holes/taps into the case itself, k.

The only other spot I tapped was in the spacer itself where the studs usually go through. An M8x1 tap didn't fit 'out of the box', but a 5/16NC18(this will tap the 'default' holes nicely) did, plus I had the tap and proper bolts handy. So I used that instead of drilling for the M8x1.

D'oh, sorry if this is getting confusing. I was just using what I had handy. But if you have to go and buy each piece, lets go with this:

In the case you could use M8x1's, just move the holes down more(post1 pic3 ref) and drill the spacer for the same size.

In a nutshell said:

So in short(if you're going shopping), you want:

a- 7mm drill bit
a- M8x1 tap

and bolts to match.

Click to expand...

Case bolts only go in 1/2" depending on spacer.
Oh yea the spacer...diatribe incoming... depends what you use. Use a piece of scrap iron if you have one, but if its 3/16" you'll need that much extra length on your bolts going in a 1/2" in the case.

For the spacer bolts even 1/2" long will do.

know what I mean? I feel I'm over-complicating this, lol.

The holes/bolts going through the side of the spacer can be whatever, just use washers.



kk, I'll re-read this to maybe cut some fat, but that's the jist of it

If anyone wants to chime in, I'd love to have any perspective on improving this overall technique.

Sorry to mix imperial lengths with metric widths, but hey, that's how Canadians got started, eh?


Let me(us) know if anything isn't clear.

Thanks for the interest btw. gl.

d'oh,
well learn the difference between to and too.

Thanks for the heads up, but aluminum is soft enough to cut without oil as long as you do 1/2 in 1/4 out 1/2 in 1/4 out, etc.... save the $$ and drill an extra 1/4" with your normal tap instead of getting bottom taps

right on Al, gotta love angle iron

You mean like what I did? I haven't had the motor off since I put it on like that, didn't need to. Its holding up good. Haven't had it off for a closer inspection, but why fix what isn't broken, eh?

Hey all! Quick update on the original post. It lasted 4 years longer than I thought it would. Went with 1/4" plate this time, should hold for another 4. You can see what was left of the old studs, they broke deep. I tried cutting a groove and using an impact driver on them, no luck.