K(0) - K6 Cylinder Head Exhaust Collers/manifolds Screw Removal

[philward]

Yet another question for the experts! I would normally just plough in with my own solutions to the problems you encounter on dealing with previous owner cock ups/bodges (as I have done for the last 40 years of biking!) but the forum members often gives you an alternative view so here's my latest problem.
I have been looking at various CR750 replica exhausts - there's a few out there that all claim to be made from the original jigs but all look different. My choice will be compromised by price etc but one issue I've noticed is the exhaust to cylinder head fitment. Some use the clamp on system using early manifolds (held in by the 2 counter sunk cross head screws) and some use the later stud attachment.
When building the last 2 engines the former cross heads have not budged (even with impact driver) and some of the cross heads where already rounded so I have just left them assuming the CR exhaust would use the manifold system (as the CR was about at early K model era).
Thats the background to the question which is:- what's the best/easy way to get these knackered and stuck countersunk screws out?
I have previously just drilled and re-tapped - is that the way you guys would go? I don't have access to welding gear for welding studs on and am not a fan of extractors - they tend to either snap (causing bigger problems) or expand the screw/stud wall into the surrounding head.
The head is now on and painted but not yet in the frame.
Your thoughts much appreciated.
Phil

[RGP750]

One Method.
You do need really good quality torx bits though,
I think from memory they are 8mm studs drill an accurate hole in the center, say 4.5mm
pick a torx bit with that dia at the core diameter, bottom of the ridges
tap in in the hole it should be a tight fit out with the 3/8" socket set and out they come (hopefully)
I haven't got time to type a disclaimer 
Good luck

[K2-K6]

I think that's quite a good method as described above, if you can get a good secure drive onto them you obviously stand much more chance, especially if the original cross drive has been butchered by PO.

My method if the crosses remain is to pien the edges in a little with a slightly dome ended punch, this closes the cross edges in a little. Use an impact driver bit and tap it in so it reforms the cross drive. So similar to above in re-establishing a competent drive means.

What I then use is a cordless drill with torque setting variability on it to drive the impact bit. Don't turn the torque up too high as the aim is to put vibration through the screw and not at this point try to undo it. Use the drill in both directions and it usually gets the screw shaken loose. You've obviously got to put enough pressure toward the screw to prevent the bit backing out. It is quite gentle and especially with things like longer case screws it avoids over torqueing the bolt shaft and snapping it off usually where the threads start. If you're patient with this method, it can get fasteners out of fairly delicate structures. Just a lot of rattling until the corrosion gives up.

[Trigger]

Never had a problem getting these little suckers out. I just use a ton of heat and smack it to break the seal of the thread.
If the head is chewed, then drill the head and use a torx bit, with even more heat.

[mike the bike]

Try tightening them before loosening.  It gets the screw to move slightly without damaging the undo - sides of the screw slots.  if you get the screw to move, spray with WD40.  Don't try to undo the screws in one hit - alternate tighten and loosening strokes to allow the WD to penetrate
Good luck, we've all been there.

[philward]

Well its defeated me so far!  blow torch heat, hammer blows and 2 broken impact bits and not one has moved a jot! Have sent for the bits recommended on an earlier thread - havn't touched the knackered screw yet as if the others don't shift, I'll buy an exhaust that uses the stubs/manifolds and leave them in!
I'm at the stage on this project where I feel I'm not making much progress - lots of research, mods and waiting to save for expensive special parts - hopefully it will be worth it though.
Problems like this just seem bigger when you're at a low on a build
Thanks for all the info and help

[Trigger]

When I mean heat Phil, you need it to be glowing red.

[philward]

I've only got a gas bottle Graham - what I use for soldering! Will wait for the new bits and have another go. Otherwise it's back to my BAE airframe fitting days drills and tapping! We weren't allowed to hammer and heat things - we couldn't even use a centre punch!

Sent from my MotoG3 using Tapatalk

[Trigger]

I've only got a gas bottle Graham - what I use for soldering! Will wait for the new bits and have another go. Otherwise it's back to my BAE airframe fitting days drills and tapping! We weren't allowed to hammer and heat things - we couldn't even use a centre punch!

Sent from my MotoG3 using Tapatalk

If someone has put retainer on the thread, your need something to get it red hot.