Asking for my friend who rebuilt a 85 Ninja 600r,

He rebuilt an engine new gaskets/piston rings etc with help from a beginner mechanic ... Engine looks sealed tight.

Finally got the engine on the bike after months. and engine turns over, but doesnt start.

Quick test showed no compression (maybe 10 max he said).

I think the mechanic said might be cam chain timing opening valves at weird times so compression doesnt go well...

Is this true? what else could it be?

and how to solve if it is the cam chain timing ... any steps to fix correctly (his manual should have it i guess)... (im sure he'll ask his mechanic boss but just wanted to get some other opinions as well)

i would say go back to basics, retime the valve train could be 180' out.

I'd also check the ignition timing just to be sure.

can't help with a how-to sorry

Aye" you say rebuilt the engine, did he grind the valve into the seats ? if so re-shimming [ if not hydrollic] to get correct clearance,