Plastic cam cover - bolt sheared off

[fatnfast]

I was swapping the plastic chrome cam sprocket covers for some nice shiney metal ones, and have manage to shear of one of the bolts flush with the head (all the other came undone really easy). There doesnt seem to be a huge amount of metal surrounding the stud, so Im not sure if a helicoil repair would work well.
This is a pic I pinched from one of steptoes guides.
Anybody had this happen and any advice on the way forward. Obviously I dont really want to remove the barrell to sort it, but if I have to.....

 

[JayC]

It's not easy to gauge the wall thickness of available material from that image but it doesn't look like much. It looks like you are right, a helicoil may not be the route to take if that is the case. Either way it needs to be drilled out first to assess the state of the thread.

I would advise that you take this to your nearest machine shop to remove the sheared bolt.

 

[fatnfast]

Thanks JayC, yes I think it could be tight to helicoil, and good advice about taking it to a machine shop but.....
........I decided to have a go a drilling it out still fitted to the bike. I was able to gauge the depth by measuring the other threaded hole, and went up slowly in drill sizes.
I resisted the temptation of using easy outs, and even put them in the outside bin! I figured if I buggered the drilling up its still sortable by a machine shop with a bit of filling and retapping. Eventually I was able to use a small punch to collapse the old threads. A run through with a tap cleaned it up quite a bit, and whilst a few threads look a bit iffy, it happly holds the allen screw at the correct torque (its only 9nm).
To make sure I coated the screw in loctite threadlock (243 coz it doesnt mind a bit of oil and still works). A quick run up, and no leaks...yet.

It looks very much like the plastic cap is basically a bung with a sealing washer, and the allen screws stop it popping out.

 

[MarkShelley]

And the moral to this story?
If it ain`t broke, don`t fix it

 

[fatnfast]

Very, very true. In my defence I was fitting some possibly pointless bling that I bought 10 years ago when I got the bike. .

 

[Pekkavee]

Very, very true. In my defence I was fitting some possibly pointless bling that I bought 10 years ago when I got the bike. .

If it ain`t broke, don`t fix it
Just ride it.
Good advice but too late for you.

Good lesson for us all.

Really those bikes don't need any bling bling.

Pekka

 

[fatnfast]

Well, not really 'to late for me' Pekka as I have had the bike for over 12 years and hope to keep it for at least the same again, so at some time it is quite possible that the head would have to come off. The seized bolt would have been discovered then.

I did order a 6mm helicoil kit a few days back, but having never used them before felt it was unlikely that there would be enough 'meat' to drill out the damaged threads ready to fit the new insert.
It arrived today, the drill is 6.3mm. The drill size for the original thread was 5mm. So effectivley I would only be removing an extra 0.65mm all around. There is enough scope to do this.
I practised on an old Yam LC side case that I have been meaning to sort for ages. It took about 10 mins to do, and I tested it by trying to pull the bolt out with the case held in a vice as well as screwing it in and out a dozen times. The insert held firm.
10 mins later, the GS is properly fixed .

 

[JayC]

Well, not really 'to late for me' Pekka as I have had the bike for over 12 years and hope to keep it for at least the same again, so at some time it is quite possible that the head would have to come off. The seized bolt would have been discovered then.

I did order a 6mm helicoil kit a few days back, but having never used them before felt it was unlikely that there would be enough 'meat' to drill out the damaged threads ready to fit the new insert.
It arrived today, the drill is 6.3mm. The drill size for the original thread was 5mm. So effectivley I would only be removing an extra 0.65mm all around. There is enough scope to do this.
I practised on an old Yam LC side case that I have been meaning to sort for ages. It took about 10 mins to do, and I tested it by trying to pull the bolt out with the case held in a vice as well as screwing it in and out a dozen times. The insert held firm.
10 mins later, the GS is properly fixed .

Yes, with the tapping drill , but then you are going to be removing a further .5mm per side when the tap takes it share of the material out.

I am guessing by now that the wall thickness at the dodgy side can be measured in a transparency value.

 

[fatnfast]

Factored that in before I started

Helicoil give min thickness in ali for a 1.5d insert as: external insert thread x 0.375.
So 0.75 x 7 = 2.625mm (7mm measured on tap and insert).
Measured mine as 2.76mm ali left (after cutting with heli tap).

In the pic originally posted its hard to see, but there is a small taper machined into the cam cover hole, so there is a more 'meat' than appears available.