Hi,
My engine broke down and the crankshaft and bores are damaged, I found a very good engine block complete with pistons from a 16V engine that had only 15TK, does anyone know if the pistons are the same with the 8valve engine? will it be a straightforward swap?
Any ideas wellcome, thanks
Simos

Just swap the engine Simos don't try to mix and match

You must tell us how the crank and bores got damaged? Oil?

I bought the bike secondhand and after riding for about 500 klms the bike started to make a knocking noise when warm, I drove it to a friends garage and borrowed a oil pressure gauge, it read 25 psi at idle and 40 psi at higher rpm so I thought it would be ok to drive home but by the time I got back everything was @#$%^@ up! When I opened the crankcase the crank is moving like there are no bearings and still the oil pressure light did not come on!!???

Got me stumped (sorry POMS)  bears with better brains will Know.
Very unusual is my only comment, got to be an anomaly at worst?
I have been on this site for a couple of years and bottom end?
New to me, chime in guys.

From what I hear these engines dont break but this one did! The bike was not being used since 2008 maybe a blocked oil passage? that makes sence since even with the bottom end completely ruined the oil light wouldnt come on 

70psi is the correct pressure for a K.  40psi would tell me there is a problem and it seems that your bottom end was well worn or damaged already.  
The oil pressure light will not light at 40psi the pressure probably would need to fall below 20psi for that to happen.
There is no substitute for a good oil pressure guage

16v pistons are not compatible with an 8v head you will bend your valves as the cutaways are not in the correct place. As Ghost said a complete used engine will be the cheapest alternative.

I found out that the 4v has a higher compression ratio and that the valve cutouts dont match, so I am on the look for a new (used) engine. There don't seem to be any availiable here in Greece so I'll have to get one from e-bay. I am not that crazy about the idea because I cannot check the engine before I buy and it's 120 euros for the transportation from Germany so if it turns out to be in bad shape I'm stuck with it. Does anyone know of a trusted source for used parts in Germany?

How about trying motoworks in the uk , they might be able to help. 
Daz