Here's my take on this.. Keep in mind I'm still young in this
hobby.. But..Cleaning an engine "per say" will never hurt it,
you may need new seals, gaskets etc... I use a tooth brush
and light solvent to clean the exterior when it starts staining
a little from burned fuel/oil and it gets most off, As it gets
worse say six mouths, year?? We have a club member that
boils the engine in Antifreeze which makes them look brand
new... And we all know what not to do with antifreeze or
containers after using it...