Blown motor

So i am not having a good week as the title would say. I am looking for a new motor for a kz750e 1983 if anyone would know of one thats working and for sale in Germany or even europe i would appreciate the help. I want to keep my bike going and no shop in Berlin is willing to do the engine work everyone says new engine. So if anyone can help please contact me. Thanks for reading

What is actually wrong with it? (any replacement is going to be a least 40 years old with no history !!)

So there is nothing to loose by taking it apart and seeing what it needs
Blown can mean a lot of things
Dave

I agree.  "Exploratory disassembly" may save a lot of trouble.

I blew the engine on my 82 kz305 last summer. Was concidering parting out the bike or getting a new engine. But ended up tearing the top end down, and found I could get it running again with a minimal amount of money. The fix was replacing the broken timing chain, 2 bent exhaust valves, new top end gaskets and seals. For around $200.00 it is up and running again. I took it on a 2 hour ride last week and it is running fine.

So i am no mechanic but this weekend i feel i will learn alot. Electrical and Electronic is more my thing. Thanks for the advice I will pull the motor this weekend not sure if i will get a chance to open it . I have a questions as i have never pulled a motor before . Firstly any advice for a newbie and do you drain the oil first a friend said no but i am opening the motor next week. Might sound stupid but asking wouldnt hurt.  I will post some pics and ask  about the damage. I am by means no professional bike mechanic but i really am broke money wise and need to fix this so if you guys and gals know a good european supplier for gaskets germany based please drop a coment. So when i get into the lower engine i will ask. Thanks for the advice i really appreciate it. 

The best advice I can offer is "keep your powder dry" what I mean by this is approach the issue pragmatically. You say that electrics/electronics is more your bag, I presume to diagnose faults you follow a process ?
Gather the information, think about what can give the symptoms you have then test in a logical sequence - mechanical issues are no different 
What symptoms do you have:

• Does it knock/rattle/make any other kind of abnormal noise ? if so does it sound "top" or "bottom" ? does the noise change when you pull the clutch lever in ?  if it sounds top, remove the cam cover and inspect the timing chain, rollers etc - if it sounds bottom, drain the oil into a clean container, remove the oil pan and inspect both for debris then post pictures
• Does it smoke ? if so what colour is the smoke ? grey is oil, black is fuel
• Did it loose power with or without any of the above ? if without noises complete a compression test

You should be able to get a good idea of what is going on before you pile into a full strip and possibly incur unnecessary costs 

Thanks its bottom end.My friend said its the crank bearing if that makes sense . I bought the bike from his mother. Really good rally family. His father was a master mechanic so i trust his advice so i am not saying what he said to me in german was right I am hopefull that was the english translation in my head and  makes sense but not honestly sure. He definitly said lower. I will post photos tomorrow. He said he would help me on sunday pull the engine. i will pull the carbs and exhaust etc tomorrow

To check things out, I would first remove the head and cylinders with the engine still in the frame. You may get lucky and find the problems and make the repairs without removing the entire engine. If bottom end repaires or complete engine replacement is needed, remove it then. It will also be a lot lighter.
You can drain the oil now, but definitely before removing the engine. Drain it through a strainer. see if any metal bits and pieces come out.
 

Only my opinion but this guy has stated "cash is tight" if he pulls the top end he is into $300-$400 buck in gaskets rings etc before any repairs. Personally I would pull the motor and split the cases, if the gods are shining on him he can do a bottom end without disturbing the top end at all - obviously a full strip and rebuild would be ideal but "cash is king" if he's really lucky a set of shells and and an oil pump may get it done ? Pulling the tensioner would allow enough lift on the crank to slide new bearings in (I have done many cars this way where the budget didn't allow for a full rebuild)

I have worked on a lot of KZ650/750 fours.

I have blown both head and base gaskets on those engines. I have also seen pistons and cylinders destroyed, but have never seen any crank or rod related issues.

I have seen a sized KZ650 engine, but the crank and rods were just fine. The bottom end on those engines is pretty robust. Crank bearings is the last thing in the world you would check on these engines.

How did your guy come to suspect crank bearing issues? Was there no oil pressure?

Injected wrote:

I have worked on a lot of KZ650/750 fours.

I have blown both head and base gaskets on those engines. I have also seen pistons and cylinders destroyed, but have never seen any crank or rod related issues.

I have seen a sized KZ650 engine, but the crank and rods were just fine. The bottom end on those engines is pretty robust. Crank bearings is the last thing in the world you would check on these engines.

How did your guy come to suspect crank bearing issues? Was there no oil pressure?

Hence why I asked the questions I did ! the OP is saying bottom end but hasn't answered my questions ref symptoms and why he thinks this ? I suspect there is likely to be a lot of wasted money here if he isn't careful !! if there is a noise at the bottom it could also be primary drive etc ????