apple watch recording time spent on motorcycle as exercise !

Hi Experts

I have recently started using my motorcycle again and have noticed that my Apple Watch (3) is recording time spent on the bike as exercise minutes! It's also recording Move effort.

It seems a bit inconsistent as it's not minute-for-minute totals but both are being updated.

I've tried all the parameters in settings for watch and the Health app on my phone (8+)... I've even unpaired and reset the watch but its still sending through the updates.

Any ideas how to stop this activity being seen as Exercise? At present I am deleting the data through the Health app on the phone after each trip but that doesn't seem like the right answer... and it's a pain!

Thanks in advance :-)

Iain