KZ440/400 cylinder sleeve O-rings

I read a post on Facebook where someone said their engine blew because they forgot to replace their cylinder sleeve O-rings. I guess they mean the big O-rings you find at the base of the cylinder sleeve. However, I can't see any cylinder sleeve O-rings in the parts diagrams for either the 400 or 440. I assumed this is because the cylinder sleeves extend down into the crankcase by a couple of inches, and so O-rings aren't needed. I will look again at my old (unusable) cylinder when it's light. I'm sure it didn't come with O-rings nor a recess to put them in, so I find what they said confusing. Anyone able to shed some light on this? Do these engines have cylinder sleeve O-rings? Am I missing something? 

Those O-rings, as used on some bikes, are to keep oil from creeping between the sleeve and the cylinder, causing a weeping oil leak.  No way an engine could blow up from missing those.

Thanks, yes, I agree. I read it again and I think the guy doesn't know what he's talking about, and the reality is he doesn't know why the engine blew. He thinks he omitted to replace cylinder sleeve O-rings (this alarmed me because I've almost completed assembly on my KZ440 engine without cylinder sleeve O-rings) so I wanted to make sure. But he also thinks this "let in air" causing engine failure. Really bizarre unless you consider he's mistaken the head gasket for "cylinder sleeve O-rings", plus he's done a "head rebuild". His post just doesn't make sense.