Thnaks guys....funnily enough Ive been working on the bike today.
I lubed the chain to see if that would make a difference to the knocking....we shall find out tomorrow.
I got the seat off within a few mins ( I just went for broke, got a screw driver in there and forced the seat off.....no breakages fortunalty!! )
I took off the locking mechanism and put it all back together *properly* this time. I put the key in and turn it a few times....everything worked fine.
Seat went on a treat, yet now I think somethings up with the cylinder in the key part of the the unit.
It does turn all the way....put after a fraction of a turn all movement in the bar that releases the catch stops.....theres no pressure so it isnt jammed......

So my next question is has anyone experienced this????

 

Maybe it's just worn , my helmet lock doesn't lock which is what I was trying to fix when I locked myself out

I think the seat catch puts the lock barrel under pressure and it wears out quickly? (Quickly being 15-20 years)

 

True....but this one a new ( but used ) replacement one I purchased to replace my broken one.....and it worked fine a number of times after being installed......

I think my CBR has it in for me lol

 

If things are installed correctly now, you need to start putting pressure on the key in the CCW direction and then straight arm the rear of the saddle directly over the catch while turning the key. You can't just turn the key, you need to release the pressure by driving the saddle down sharply.