Looking at your picture links, the machine is designed with no air filter.
Being a snow blower, there's no dirt kicked up that could be sucked in to the engine.
Just like a an outboard boat engine, no air filter.
Regarding idle RPM's, just a good steady low RPM that with the rotating
part of the machine turning, the engine doesn't stall. This isn't terribly important.
Max RPMs will likely be 3,600 RPMs.
You don't want to go above that as it'll shorten the life of the engine and wear parts of the machine prematurely.
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