trying to loosen various nuts/bolts on the engine/frame to allow me to attach a belly pan to my z750 but they all seem to be totally jammed. beyond a spray of WD40 on them which i will try tomorrow does anyone have any other advice? or might i need to take it to a garage so they can have a go with some sort of super-spanner?
Rattle gun (Impact Wrench), usually does the trick … possibly hire one?
or heat up the area spray on some WD40 let it soak in and give it a sharp hard crack
plusgas is much better tan wd40
Nice one! Not heard of it before
http://www.lawson-his.co.uk/scripts/details.php?cat=Penetrating%20Oils&product=30700
KY Jelly, normally loosens things up.
Shock them first and if that doesnt work then heat them up.
When you come to putting them back in ALLWAYS use grease on bolts that go into metal, It makes life so much easy if you ever need to take the bolts out again and it keeps them in good condition so you dont have to replace them.
Have you got a breaker bar? - you attach a socket on the end of it and the extra leverage usually does the trick. You can buy them in Halfords.
actually, i’ve been looking for an excuse to buy a proper socket set so maybe now is the time to invest… perhaps i am even old enough for my own toolbox now as well 
use plus-gas or similar penetrating oil and possibly an impact driver (they often have 1/2" drives on them) and when you reasemble use copper slip grease (just a smidgin, and NOT on wheel bolts , should you have them) don’t forget that bolt torques are allways given for a clean DRY thread unless otherwise stated. If you use copperslip then do them tight, but if you are going to use a torque wrench then you need to reduce the setting by up to 1/3rd!
Good advice Kenny, wish there more like you around.
I’ve had my rant about crappy use of impact drivers on the forum before, but when all else fails, go for them. Just spend a bit more and get one with adjustable torque if your going to use it (heaven forbid) for tightening.
I’ll stick with my “tool of last resort”. (Ignoringing the lump hammer and cold chisel!) They do have their uses, but only after the PlusGas and the breaker bar have failed.
with plusgas /wd40 you need to leave it overnight and then maybe spray a second time…it you suspect rust due to the age then even longer can help but apply a bit of gentle heat first…air dryer will suffice. If not wait 24 hours then get your flat sided socket set, not the set with the multiple internal edges…and give it a sharp crack with a hammer on the solid bar attachment, not the ratchet bar…not too many times as all you need to do is break the seal…it can help to tighten it a tad first…air tools are best for ruining your nuts and making your life easier but who has home air tools…also be very very wary of grease on bolts on major components, vibration can remove them if your not very very sparing with the grease…
We use a product call Rost Off Ice made by Wurth, basically freezes the thread area and creates cracks in the rust - opposite to heating them up.
becareful some of the long engine bolts , go into the ally on the sides but run in a groove exposed to the outside world in the middle , have a look and give it a spray in that area too , but if they are really stuck i have known them to crack the cases on the way out …
if your not a million miles from me i have one of those impact thingys you can use .