[litnin]

Where did you see that it says in a Honda shop or owners manual
that it's fine to use any synthetic blend that's not energy conserving?

Every Honda motorcycle shop manual that I have says

Recommended Engine Oil:
Honda GN4 or HP4 4-stroke oil or equivalent motorcycle oil with an
API service classification SF or SG Viscosity: SAE 10W-40

The GN4 is conventional and the HP4 is the synthetic blend.

The newer manuals are calling for 10W-30, but I've never seen one
say that any synthetic blend, non energy conserving is fine.

 

[litnin]

Ammmm.... just bought a Castrol GPS 10w40 with all the trimmings and adulations on the bottle. It says "for four stroke motorcycle engines", it has a motorcycle engine on it, it "said" to have newest technologies blablabla...

You guys scare me. What can be wrong with that?!

Read for yourself

Going strictly what the original poster said, they did not use this oil, they
used regular Castrol synthetic blend.
They specifically said they called Castrol and Castrol told them to use
the "motorcycle oil" synthetic blend.
That tells me they used regular off the shelf automobile oil... Not the motorcycle specific oil that you have listed here.

The oil you have listed here is probably fine.

 

[litnin]

Please note that is an inline engine pictured on the bottle not a V-twin.

Noticed that, but It's four stroke motorcycle engine oil
So it doesn't suit? Damn, now I'm totally confused...

I think he was just making a joke.

It doesn't matter.