Does buying a motorcycle from a private seller w/ registration automatically cancel the registration?

I'm selling my Honda Grom to a buyer and was wondering if he buys my bike, will my registration automatically get terminated after I sign the title over? Because a friend told me even if the registration is up to date, it gets terminated after selling it because the new owner will have to register anyways.

I ask because my bike registration has been expired since August 2018.

Not until you turn the plates in.

You must also cover your donkey by reporting the transfer to your title authority.
NEVER rely on others to take care of YOUR business.

Not until the new owner transfer the title at the DMV.

If you're in the UK you get the buyer to fill in the V5 registration document and sign it which you send off the DVLA in Swansea. The address is provided on the back.
Then you make him/her fill in the green slip which he retains for the purpose of tax and insurance until the new V5 document comes back in his name which could take a month, but is usually settled between 10 and 20 days.
It is a legal requirement that the buyer insures and taxes the vehicle before riding away, but not YOUR job to enforce it.
However, I advise giving him a duplicate sales receipt and make sure you note the time and date the vehicle changed hands to cover yourself from prosecution if he's involved in an incident later.

No. How is the DMV going to know "the second you sign your title over"? You have to notify the DMV that you no longer own the vehicle, or you will remain responsible for it until the new owner registers it.

Check your local laws! I suggest this because Connecticut requires the plates to be turned in. Some states require the seller to notify the DMV. Lastly there's a possibility that the vehicle could be used for a crime, unless documentation exists this can cause legal problems.
Also some states refund the remaining registration period money.

It does if the new owner goes and immediately retitle and registers the bike. But if because there's a tag unexpired on the bike and they drive it around. When selling vehicles it is smart to take a trip to the title office and fill out their paperwork for release of liability to cover your a**.

The new owner filing the transferred title / registration at DMV will supersede the previous title / registration. How on earth would DMV know when you sign something outside of the DMV office? Like wow, dude. In the law nothing happens "automatically" except death. Even then, it helps to have a death certificate.

No, you need to file a sale notification or you can be held responsible for anything the new owner does with the vehicle including but not limited to camera tickets, parking tickets or accidents.

No. Your registration isn't terminated until you notify DMV and surrender the plate. The registration may have expired, but it's not terminated.