Before you say i was tightening it up too much - i was not. I never even got to the the washer touching the sump plate. It is basically a case of buying absolute cr#p from Fleabay. i bought a magnetic sump plug in June 2018 & did oil change. It was then done again July 2019. Last night i went to screw the sump plug in for its 3rd time in its life and it didnt seem to start to tighten so took socket off it & the bolt head & some of the bolt thread were just resting in the socket. Washer was untouched.

Apart from laying bike on its side and trying to gently try tap the bolt out in reverse or try to get a slit in it to get a flat head in & reverse it... Any more ideas. ' chewing gum & let it set & try to un-wind it !!''

 

So the head broke off the plug and there are still some threads stuck in the oil pan hole?
Was the plug aluminum or steel?

if it's steel:
If there are enough threads, maybe try a vice-grips or a pipe wrench.
Slot the threads and use a large screw driver to try and remove it.
If you have a welder, weld a blob on the steel threads.
Heating expands the metal, then it will shrink when it cools and will loosen.
Then you might be able to spin out the remaining threads.

If it's aluminum, it's has probably galled and seized, it will be very hard to get out.
I'd probably start by taking the pan off and working on it on a bench.
Drill the largest hole possible and use a big easy out.
Or cut a slot up the inside of the hole and try to split piece and knock it out with a chisel.
Or buy a new oil pan.

This is one of those things where there isn't one sure fire way to do it.
You'll just have to try a few things and eventually something will work.

 

Cheers Phil

thanks for all your ideas. we will be attacking it next saturday. Not sure of the type of metal . The saving grace is that this bike does have a sump pan. When i bought it 2nd hand years ago & did an oil change, the sump plug at hte time was just spinning in the pan & not tightening up. I managed to get a second hand pan for a few quid off Fleabay.
Had this been the suzuki SV 650 that has no separate pan then who knows what could have been the end result ££££££

a

 

Update - The bike is up & running
Mate came round. We laid the bike on her side & managed to get the old sump plug out. It was a hollow bolt as it had a magnet on the inside of it so had the worlds flimsiest/crap thin thread metal running round the outside of the magnet. Wedged a small screw driver in & turned the thread back out. Pushing screw driver up inside the flimsey thread pushed magnet into sump plate BUT it sat just on the top so a small screw driver poked in & the magnet jumped onto it & suck great . Like 'Hook A Duck' at the fairground !!.
Replaced with a Honda genuine part from David Silvers.
Note to self - BUY Genuine.