500 Two-Stroke Tech

Hi.
I am wondering if the coils are earthed by black wire enoughs and they are bolted just for solid and neat assemby,
or the bolts are really needed for grounding.

Thanks for explaining me.

Earthing is needed, but only for the primary side of the coil.
On the secondary side, the two plugs are serialized, so no earthing needed for this side.

So at the end of the day, can I just fasten coil to the bike or steel bracket + bolts are mandatory for good working of the coils?

Reminder to all on the coils, they are often cracked and have a bad earth, took a year of trouble shooting and a tip from a forum member before fixing.