Ahh yes I misunderstood, sorry
usually not much of a risk, no
increased wear and suboptimal parts (preworn and wallowed out engine)
can cause a failure you would otherwise have to expect much later and likely less violent,
but apart from that no..
the valves even of an L Head should keep you from revving into dangerous realms
(means they should keep you within 5000 to 5500 rpms max,
which is usually safe for engine internals in good condition.
how good the internal condition is we can't tell.
it's your health and I wouldn't dare to make that decision for you.
Personally with a mystery engine (unknown running hours and maintenance)
and since you have to crack that eggshell in order to remove the governor,
I personally would take that opportunity to settle in on a confidence level for the internal parts (by measuring their wear) and then decide what to do and what not to.
And to be frank,
that takes longer than waiting for parts and reinstalling the governor lever and stuff.
and it requires some good quality tools (especially measuring tools)
The crude easy check:
wiggle the crank up down front and back left and right, and if that is already beyond the specs (see manual)
be prepared for some serious amount of work..
if that's fine and the compression of the engine is still good
I personally would lean towards "it's likely safe to rev up to 5k"
aways in mind, that a sane person would always stop and reconsider if the engine starts to make weird noises
But again, your health, not mine...
I haven't even touched the engine,
how can I tell you what risk to take?
I'm safe here, half way across the globe and talking is easy
'sid
PS Short: if you're not confident the engine is in good shape, just dial in for safety,
once you feel confident to check the engine thoroughly you can always step up the game
