Depends on what one means by pollution. Excluding CO2 and H2O (these are natural products of combustion), the other gases like nitrous oxide, CO, and unburnt fuel are considered pollutants.
Cars have catalytic converters, which burn up those nasties and emit very little other than CO2 and H2O. Small engines don’t have catalytic converters - or the combustion mixture controls that modern fuel injected engines have. As a result they emit, raw, what exits the combustion chamber.
And besides that:
Bumblebees can not fly!!