Hi John, I've come across some incredibly dirty snorkels. Some can be as much as two-thirds coated with fine dirt on the inside. This can happen even if the filter is maintained, if people are mowing in extremely dry and dusty conditions. Just like the old Colgate ad once claimed "It gets in". Very fine dust eventually penetrates even the best air filter. If there are clay molecules in the soil these can solidify over time in the folds of the snorkel. Over many years they can form a solid mass. And as you suggest, many snorkels develop small cracks and leaks and start sucking air directly from the outside, which is very bad for the engine. Larger grit particles like sand can get sucked straight into the engine. Several months ago I restored an old Southern Cross engine that must have been used in very sandy conditions on the coast. The sand was in everything, right through the carby and into the sump. So it is important to inspect snorkels every so often. Your advice is spot on.
