Z1OwnersClub GB

I changed the guides in my 900A4 head for the iron guides used in the later thous. I re-cut the seats. The other day I was lapping in the valves ready to reassemble and having nipped .3mm off the stems. When I came to do the exhausts, the faces turned out to be more pitted than I expected considering the bike was pulling really well before I stripped it for cleaning and a performance upgrade. I ordered up a set of pattern valves which arrived yesterday. I noticed that the thousand has different valves, which annoyingly my supplier doesn’t keep in the UK warehouse. Are the 900 valves a material not suited to iron guides? I thought they were the same size, but there must be some difference?

The early original OEM square keeper valves are a different material to the later round keeper ones and are not compatible with the later cast iron guides.
You can use the later round keeper valves in both the early bronze and later cast iron though.
The early OEM bronze guides should be avoided anyway unless you must as they were made from an inferior bronze alloy and are prone to excessive wear and the whole lot should be replaced with the later parts if doing a complete overhaul..

Thanks for the reply mate. That was what I thought, but I was hoping I was wrong - bugger!