In Canada, I’m pretty sure we’re ok to run older cylinders. We’re supposed to have the clutch/steel gear update, new airbox, and 8.5 carb – which many of the engines with older cylinders won’t have.
If you’re buying an older one, there’s also normally no telling how many hours it really has on it, so you’re almost obliged to have the seal broken and inspected, in which case, you’d may as well refresh the top end.
Your best bet when buying a Rotax Max is definitely to get a completely updated engine – preferably with passport to see when it was last sealed (generally a reasonable indication of how many hours might be on the engine). Otherwise, what seems like a “deal”, can turn expensive when you bring it up to current specs.
There’s lots of “good” deals (and truly bad ones) on karts with out-of-spec Rotax engines up here in Canada where Rotax is about all we have for 2-cycle racing. I’ve been looking to get some friends into Rotax, and the first questions I ask when shopping for them is whether the engines are updated.