already been done, was the very first thing i done when i realised it was stuck on really well

yea pikey dan, im leaving that as my last option, im gonna re-try the impact driver, see if i can get any purchase on the bolt. If that still fails ill nip to the garage, and failing that ill see if i can get something welded to the bolt.

Right... No offence is meant by this statement:

This appears to be beyond your skills and/or equipment level.. in which case take it to a local engineering firm! It will be out in 5minutes and wont cost you much..
No doubt they will just TIG a piece of bar on, and then use that to untighten it, helped by the heat!

Please note i said "engineering firm", do not confuse this with "bike shop" of any form!

This is a very common occurance in engineering (and mostly preventable on initial fitment!)

And a daft question... that picture shows writing saying "10mm allen key"... to check, you have tried uptightening that bit havent you?

the outer 10mm key is the self extractor, so tightening it would just make it more difficult to remove the inner 8mm. if anything i would say undo and remove the self extractor completely, then see if you can work the crank bolt loose, before re fitting the extractor to pull the crank arm off.
also if you use a pnuematic impact driver, make sure you use impact rated parts with it, as normal crv parts can shatter.
i think the best way, if you can, is to weld something on there and get a lot of leverage on it

Dude, i had this problem.  I snapped my cranks leaving nearly the whole axel on the drive side arm.  It was the same story....all rounded and knackered.  Here's what i did.

-Drilled out the crappy alloy extracting bolt, careful not to damage the outer threads as you can buy a new one from crc for 4quid and have it all as new again.

-Buy a brand new drill bit from a decent shop (Ti coated etc, not a cheap one!) and drill down into the inner/steel crank bolt, there's already a small hole through it, so its pretty easy with some effort and a good drill bit.

- Now, go to halfords or similar and buy an eazi-out set, i bought a 'lazer' one about 15quid, for a few different sizes.

-Use a decent socket and ratchet to work the eazi-out in, once it bites stop for a minute.  You need to really gently 'crack' the threads to break the join thats causing the seizure.  Give it a go, a really powerful, steady, controlled turn.

Now it should go.  I have used these to remove broken spark plugs from engine heads, thats tough, this does work if conditons are good!

Now, despite all my efforts in my case, i just couldnt get it to bite, i cocked up in previous steps and drilled the hole too big, a little to big for my easzi-outs (prat!)

So,

I took a junior hacksaw blade and cut gently down to the axel, i cut two cuts in a triangle so that there was a loose 'wedge' in the bolt, it was still stuck to i gave it a whack with a metal punch, hey presto the wedge came out, leaving a chuck on exposed thread, from here bang a load more wd-40 or ideally 'plus gas' and give it a whack on the exposed edge with a flat head screw driver, it cannot hold any more, not a chance.  Worst case is that you need to whack the bolt to bend it out of its round shape, towards the middle of the hole.

Then it will come out, i guarantee you.

After replacing the outer removal cap and bolt the cranks looked un-touched and as before, then i sold it on here as a spare (because the non-drive axel was snapped)  I made this clear in the add, but it made no difference anyway.

It takes time, patience and some decent tools.

But it can be done.

Hope that helps!

funny question but, did you torque it up or just do it up as tight as possible?

in any instance, everybody running thousands of pounds worth of kit should invest in a £50 torque wrench!!

nope was toqued correctly, ive got a shiny chrome one in my garage that my granda gave me, like was said, invaluable. Trust me i donw everything right when installing it, which is why its puzzling me.

well they told me to do one when mine snapped. great for one of the most expensive extreme use chainsets you can buy!!

good luck

Your clearly not a competent mechanic and an even less skilled engineer so stop with the abuse towards people who can actually undo an 8mm bolt without ruining it. It's nobodys fault bar your own so quit the abuse towards people offering you advice which you seem to just be ignoring.

Heat up the crankarm and bolt and hope that the difference in expansion is enough to break the seal free on the job. You can either try this whilst using a Torx bit or, ideally, kill two birds with one stone and have a decent bit of stock welded to the bolt which you can use to loosen the bolt. The heat generated from the welding process will be sufficient to free the bolt.

You did remove the 10mm auto-extractor fitting first I hope - If the crank arm is stuck to the axle thats a whole different problem but relying on the 8mm bolt to remove said arm isn't the best answer and might explain this situation.

FWIW, soaking it in WD40 is about as much use as soaking it in spermicidal lubricant in engineering terms. Use plus gas or something with penetrative qualitys greater than that of a water melon for maximum results.

Welding isn't a big job, steel welding requires no special set up or anything else, I can think of countless local shops which would weld something onto that bolt for free, whilst you wait.. You don't need to travel 100 miles and you don't need a welder. Turn up at your local engineering workshop and ask the man nicely..

Sorry to sound like I'm ranting - Edd gave you some good suggestions and his comment of asking whether it was fitted properly was perfectly reasonable - you rounded the bolt and the allen key.