Golf engine clunking sound after rebuild

[gogogolf]

I recently removed the head from a 1.4 golf ABD engine to replace the head gasket. Whilst I had the head off I stripped it to decoke the valves. On replacing the head I aligned the timing marks. Now when I start the car up, it runs but there is an occasional clunking sound which jolts the engine and gearbox - the problem seems worse at idle than when revs are applied. What is it likely to be? Suggestions appreciated.

[spainy]

Have all the covers gone back on right and bolts in the right places. Some years back did a head on a polo and had similar problem turned out to be catching on timing belt covers. Good luck

[Crasher]

Did you fit new hydraulic tappets?

[gogogolf]

Thanks for your suggestions. I reused the original tappets as they were not noisy before. Is it best practice to replace these on a rebuld? I have checked the timing belt covers and refitted them. I also took out the spark plugs, one seemed not to have been firing as it still looked clean, so I put the old set back in. Everything seems to be running fine now.

[Crasher]

I wondered if one of the tappets may have been sticking, they don't like being taken out and re-used. At around £10 each it is also false economy, if one jacks open and hits a valve... Mind you, that only tends to happen on the 16v 1.8/2.0 type head.