Problems with Hyundai Accent Prime 1.5 Diesel 2006

Hello colleagues, I'm having problems with the three-cylinder diesel engine in my Accent Primer. The engine was recently rebuilt, but I've noticed it vibrates a lot at idle. I don't know if this is normal for these three-cylinder models. The engine mounts were replaced, and the timing on the counterweight housing was checked. My question is this: the timing marks on the counterweight gear are clearly visible, but on the crankshaft gear, there's a small mark on one tooth, like a knock; you have to look at it with a magnifying glass, and it's not a clear mark. Is there another way to time the counterweights? How can I tell if the assembly is properly timed, or is it normal for the engine to vibrate a little at idle?