Removing Exhaust Bolts

I want to remove the front downpipe on my K6 (to replace it with a better one). I have just had a look at the fitting arrangement and see there are 2 Allen bolts going in to the aluminium cylinder head. The specified torque is 23 NM but these two have not moved for 13 years, so I suspect it will take a bit more turning force than that to get them out. I just tried a 6mm internal hexagon with a 3/8" ratchet (with a very small amount of force) - and rather than risk damaging the bolt heads I've sprayed on some penetrating oil and will leave it a while.

Would anyone that has done this job recently drop me a line and let me know if there are any pitfalls I should watch out for? Any advice would be much appreciated.

Alan

I've been reading a few previous threads about troublesome studs - but I'm guessing they refer to older models as the K6 has Allen bolts.

Here is a photo of the problem:



I can see now that the manifold bracket has almost completely evaporated at the top. The two Allen bolts seem to be in okay condition but I'm loath to apply too much force until I've done all I can to assist them coming out without too much of a fight.

I'm in no rush about this job (I was not going to tax the bike until April) so I can take my time. I have sprayed the area around the two bolts with WD40 to see if that penetrates, but gravity is against me. I'm happy to take my time.

I could just try tapping in a 6mm hex to make sure it is really well seated, then applying a bit of force with a long tommy bar. The risk is that the internal hex might round off or the head might snap. If it rounds off leaving the bolt head in place I suppose I might be able to get a stud extractor of some sort onto it. Would one like this be suitable (this is not something I've come across previously):

https://www.ebay.co.uk/itm/SEALEY-VS...rk:12:razz:f:0

If the head breaks off then it might leave about a 10mm shaft where the clamp plate is at the moment - again perhaps a stud extractor would work on that?

Another option might be to weld an Allen key into the bolt?

If all fails I could probably drill and left handed tap the remaining part of the bolt out - I've done that before and have the equipment here, but I'd rather avoid it into aluminium if I can.

I'd appreciate any advice regarding preparation (penetrating liquid, heat &c) and the best type of stud extractor to have at the ready would be much appreciated before I start.

Best wishes,

Alan

[SV650rules]

Heat, and use a proper penetrating oil ( WD40 is a water dispersant ) like plusgas as it will find its way into smallest gap by capillary action, and may be worth tapping the head of Allen bolts with hammer before trying to remove them as this can break the grip of the thread a bit, and especially good if rust under bolt head that may crumble and free up the bolt.

Good luck...... stainless bolts are pretty much always low carbon / low tensile so not as strong as normal bolts, but the lack of thread corrosion may help, although stainless bolts can gall up easily.

If you look at previous threads people have had most success removing sheared bolts and studs with a reverse twist drill rotating anti-clockwise, which tries to unscrew a RH thread as it bites into stud ( links in AdamElf previous thread recently IIRC ).

Originally Posted by SV650rules

Heat, and use a proper penetrating oil ( WD40 is a water dispersant ) like plusgas as it will find its way into smallest gap by capillary action, and may be worth tapping the head of Allen bolts with hammer before trying to remove them as this can break the grip of the thread a bit, and especially good if rust under bolt head that may crumble and free up the bolt.

Good luck...... stainless bolts are pretty much always low carbon / low tensile so not as strong as normal bolts, but the last of thread corrosion may help, although stainless bolts can gall up easily.

If you look at previous threads people have had most success removing sheared bolts and studs with a reverse twist drill rotating anti-clockwise, which tries to unscrew a RH thread as it bites into stud ( links in AdamElf previous thread recently IIRC ).

Many thanks, I'll pop out and get some proper penetrating oil this morn and let it soak for a few days before I try anything. I was wondering whether an impact driver might work (if I could find a 6mm hex that would fit into the drive) - or would that be too aggressive?

Alan

[SV650rules]

Originally Posted by Othen

Many thanks, I'll pop out and get some proper penetrating oil this morn and let it soak for a few days before I try anything. I was wondering whether an impact driver might work (if I could find a 6mm hex that would fit into the drive) - or would that be too aggressive?

Alan

A quick shock like an impact driver is often much more effective than a slow application of torque, also the driver puts a downward force on the bolt head which is similar to the tapping with a hammer I mentioned, which can help break the grip of thread. There are hex attachments for impact drivers, my Halfords driver has a set of bits with it including hex bits.

Originally Posted by SV650rules

A quick shock like an impact driver is often much more effective than a slow application of torque, also the driver puts a downward force on the bolt head which is similar to the tapping with a hammer I mentioned, which can help break the grip of thread. There are hex attachments for impact drivers, my Halfords driver has a set of bits with it including hex bits.

Thank you again. I've just been out to get penetrating oil and will spray in twice a day for a few days.
The impact driver route might be a good one as the bolt heads are easily accessible. I'm sure I have one somewhere here.
Alan

[R1ffR4ff]

All good advice and I keep one of these in my Garage for jobs like this,

https://www.ebay.co.uk/itm/Butane-Ga...:rk:6:razz:f:0

Puts the heat exactly where you need it.Also I always wire brush off corrosion and try to slightly tighten rusted bolts before trying to undo them as it cracks the corrosion seal after a penetrating oil/solution has been left to soak on them.

HTH

[Seeker]

If the worst happens, don't use a stud extractor, buy a left handed drill bit. The act of drilling with such a bit will usually release the stud. A broken stud extractor can be a nightmare to remove.

Originally Posted by R1ffR4ff

All good advice and I keep one of these in my Garage for jobs like this,

https://www.ebay.co.uk/itm/Butane-Ga...:rk:6:razz:f:0

Puts the heat exactly where you need it.Also I always wire brush off corrosion and try to slightly tighten rusted bolts before trying to undo them as it cracks the corrosion seal after a penetrating oil/solution has been left to soak on them.

HTH

Many thanks, I have the same and will try it in a day or two once the oil has had a chance to seep in.

I'm tempted to try a windy gun, I have one that came with a compressor which is quite good for doing up wheel nuts but I have not tried it on anything else. I tending to think it might be a bit aggressive and perhaps shear off the bolt heads. I've found my impact driver in the garage unfortunately it doesn't have any hex bits, but the Halfords one mentioned above is quite cheap.

Alan

Originally Posted by Seeker

If the worst happens, don't use a stud extractor, buy a left handed drill bit. The act of drilling with such a bit will usually release the stud. A broken stud extractor can be a nightmare to remove.

... that is why I was thinking of this type of stud extractor, which fits externally:

https://www.ebay.co.uk/itm/SEALEY-VS...53.m1438.l2649

I have not used one of these before, it looks like it just has a cam that tightens up as it is screwed to the left. Clever, but does it work?