Cranks are my largest spares worry- mine has about 50 miles on it now and I have a serviceable spare, so I've enough for two of our very short seasons at least. There were rumors of them being rebuildable by someone but I haven't found a source yet... It looks like the problem is the inner webs have the crank pin cast into them, so the entire wheel would have to be remade to service the pin were it worn past spec. At least they last a little longer than the TZ units Piston, rings and wrist pins are available aftermarket, and most of the gaskets and minor engine internals can be made or repaired if NOS isn't available. But the cranks.... they are vanishing and getting ever more expensive.