Reading Fugazi's earlier description of the problem with his engine, I think some are jumping down the wrong path assuming the problem was corrosion of the waterways.
His problem ( as described in an earlier post ) was corrosion of a washer causing the water to enter the crankcase and mix with the oil.
I hear the cries of "what has this to do with engine being 4 stroke or 2 stroke" and indeed this probably has nothing to do with the fact the engine was 4 stroke ( although I can think of many reasons it would have a worst affect on a 4 stroke than a 2 stroke engine, but will leave that to those who evidently have superior knowledge on the subject ).
However, it cannot be disputed that the rebuild process does incur far more cost. ( says Paul D with his last Honda bill for