HELP on something wrong

[porschekz]

Hi Gents,
I just finnished the full refurbish of my 80s engine (new rings, valves, seals, tensioners, carburator cleaning, etc). It restarted very well butt with an inestable idle range. I restarted it several time w/o any problem and even I gave a short round of hundred meters running well to check the gearbox, clutch and brakes.

When I was back to the shop I checked the ignition advance and I observed that it was to retarded. However when I tried to modify the static advance I made something wrong moving backward (anti clockwise the engine ONLY around 20°) to fix the right advance point. Afterward it restart quite well but after few second running perfectly it started to runt budly (like with some cylinder failing). When It tryed to restart it looks like some cylinder where failing and when I heard like some "clonk" in the motor I stoped it inmediately. Later it doesnt started again however I already checked that all the sparkplug are fairing well.

Something was wrong but I don t now how I can found where is the problem. It looks like it lost the distribution adjustament??. If this the case why moving backward the engine few degrees it could lost the adjustment?. I made several times this bad operation in my multicilinders KZs (400,650 &1000) and never I'v had any problem further.

I expect to remove the engine from the bike and to put it in a frame for a better handling and later to check everything.Therefore some urgent need and sugestions are welcome:
How I need to found where is the problem?
If the problem cames from the distribution adjustaments, how I can check that it is wrong\ok. How and what I need to dissasembly to test the whole distribution? Is it necesary to disassembly the whole engine including the head to check that everything is ok?

Any other sugestion should be warmly welcome since I have totally shocked.

Cheers, Juan