Dave can you please describe how to remove valve spring retainer clips ( 110 FZ ) in order to take valves out ? I also have a problem about removing the disc valve, seems like disc valve pin retainers are stuck, is there an easy way to remove them ?

Thanks in advance.

We have special tools to compress the valve springs to remove the keepers. Without these types of tools it is difficult. The valve must be held against the seat and then you can compress the spring and remove the keeper. You should have extra parts on hand as there will be springs and keepers shooting around your workshop.

Have you removed the set screws holding the disc pin in place? There are two of them, one on top of the other.