Overhauling the valves and valve train? check the camshaft lobes for wear and/or damage, worn valve-guides can cause smoke on start up and a loss of performance? The Cam-chain, tensioners and guides should be renewed as a matter of course.
Some of the more important parts that should be considered are this component and perhaps some of those listed below:
Order all the items you require at the same time, new valve-guides 12204MAT305 valve stem seals 12209KE8005 valve retention cotters 14781MAT000 & valve lifters 14731MT4010 for example, and save money by avoiding multiple shipping charges.
Try this pro-workshop gasket sealant: 08C70K0234M.
Please be aware that this component may have other applications within the Honda model range, so check the part-number is correct prior to ordering?