my dad let me ride his harley davidson xl 1200 why are the gear so clunky and why is the bike so heavy for only being a 1200?

The trans shouldn't clunk, even if that is the reputation.

Percieved weight isn't always weight. It's often the center of gravity.

The Japanese motorcycle is made of plastic and pot metal and so is lighter

The Harley is steel , chromoly and magnesium alloy , that's part of the reason you see 50 + year old Harleys still on the road but after 10 or 15 years Hondas are scrap .

As far as the transmission , my 1200 shifts quite smoothly , even with a sidecar attached to it .

Maybe you need oil , a clutch adjustment or the primary chain is loose ?

you test rode a plastic and aluminium machine. That HD is made of heavier steel. It should NOT have clunky shifting though. Check the primary fluid and chain. Possibly needs the clutch adjusted. As a matter of fact you shouldnt even be able to hear it shift. They are that smooth.

Oh! You missed looking at the tank badge...Go back out and gaze at it for a minute or two. That will make it lighter and shift better!

Five minutes or more and it should be faster, more "torquey ", a marvel of 1920's engineered single pin crank, and have soul leaking out on the floor.

BTW I test rode a Honda interstate I think it was a 1300 and it felt so much lighter. Edit I dont hate Harley I just like the metrics better but the 2014 interstate is lighter and I figures out there is something wrong with the transmission

Why would you not expect a 1200 to be heavy?

btw I think you are feeling a difference in weight distribution.