hold on -- engines on a dyno are under load (that's what a dyno is---a calculated load device.)
Of course you could remove the load but pork a?
Ideally the load matches the intended (design parameter) load
On these little aircooled (actually fuel cooled ) things - you run em up n down the load (thru the rpm band -a and make sure they don't overheat .
I run mine from square one -on the pipe with the prop I will use just vary the load so the engine does not overheat .
The only time I use a bench -is in sorting out prop/pipe combos