Cylinder stud bolt threads damaged

[Einar]

While I was torquing my valves to 35Nm, the bottom front cylinder stud bold started coming out of the block (about 1 cm), and I have confirmed broken threads and JB Weld repair.

I am unable to unscrew the stud bolt with my available tools, but I did managed to screw it back inside with some fresh JB Weld.

The JB Weld solution successfully holds 12 Nm torque (I have tested until breaking point).

Question:

1) Am I crazy to drive with one bolt torqued to 12Nm? (It shoud be 36Nm, none of the bolts felt torqued when i dismantled, maybe because of this problem?...)

2) Is there an everyday tool (something I might have) that I can use to remove the bolt without damaging it too much?

3) Any experience on using "time serts (?)". I have seen Chris Harris' youtube video where he uses that as a solution.

Just another day in bike-restoring-paradise!!

[Barry]

Perhaps not a very helpful comment at this stage but I wouldn't torque to 34Nm (25ftlb). I've always stopped short at 30Nm (22 ftlb) and that's not caused a problem.

12 Nm is surely too low. I suspect that the expansion and combustion forces would pull the stud again once the engine was run and you would risk distorting the head due to uneven clamping forces.

Double nutting solvent cleaned threads is the the usual stud removal method although there are proper stud removal tools that incorporate a cam action like a pipe wrench to grip the stud.

If it's any help I've attached a services bulletin which indicates that thread repair is a common process and was even done by the factory.

[montmil]

...Double nutting solvent cleaned threads is the the usual stud removal method...

As Barry recommends, clean the threads and double-nut the stud. Back it out using a box-end wrench or a socket. Use caution not to put a bending load on the long stud. Keep it straight.

You're going to have to remove the stud sooner or later. Back it out and call it done. No biggie.

[Einar]

I was hoping I could fire her up to test that all works (I just changed piston + pushrod seals) before I strip it back down to do the repair, would that be ok?

Double nutting will do the trick, of course. Good tip!
So seems like I have to Helicoil it. After watching on youtube it looks feasible even for me.

1) Would a kit like this include everything I need (I have a drill) ?
http://www.ebay.com/itm/V-Coil-Thread-Insert-Repair-Kit-M10x1-25-Compatible-With-Helicoil-Spark-Plug-/331788936660?hash=item4d402965d4:g:9zMAAOxyYANTXiGR

2) I believe the stud diameter is 10mm, does anyone know what the thread size is?

Roger on the torque values, I will adjust accordingly!
Thanks.

[mrclubike]

I remember when I was a mechanic at a Tool rental yard and I would overhaul Bosch electric jack hammers
They had Helicoils in all the threaded holes in them from the factory
But I prefer solid type thread inserts instead of  the coil type  

[Barry]

2) I believe the stud diameter is 10mm, does anyone know what the thread size is?

It's M10 x 1.5  

[Einar]

Fantastic! Thank you for the feedback! Will get my helicoil kit off ebay and do the repair.

[Tony Smith]

Fantastic! Thank you for the feedback! Will get my helicoil kit off ebay and do the repair.

Be careful that the thread pitch matches. although the ISO standard for M10 threads is 1.5mm coarse and 1.25mm fine, the world and dog seem to have standardised on 1.25mm pitch. That is to say 1.25mm pitch is much, much more common - make sure that you get the right one.
 
Also, when you buy your drill, buy the very best one you can afford and.as I mentioned elsewhere, in the absence of a drill guide, have a friend check your alignment before you pull the trigger on the drill and while you are drilling.


All is not lost if you do end up with the hole a little angled, you put the stud in and then bend it more or less into alignment - but let me tell you this was a lot, lot easier with VW studs which were simple bright mild steel, ours, for better or worse, are a stronger breed of steel with a much higher elasticity modulus.  (means the buggers are hard to get to take a permanent bend - so get the drilling right).