top end rattle

[nw69fl]

I have a 72 sportster that has a rattle in the top end. It happens when I decelerate. It sounds like the battery case is hitting the back rocker arm cover but ir isn't. Any ideas? Does this sound like something in the rocker assembly or in the valve train?

[wreck74]

could be a broken rear motor mount.

[saltcaveminer]

before tearing into the engine, check for loose bolts (seat,fuel tank, chain,motor mounts,etc.Salty

[olpigiron]

          As Both wreck74 Said, And saltcaveminer Said,
        And This Is Way Out In Left Field, But Also Look @
Rear Sprocket Rivets. I Know It's Not Top End, But U Never Know.
                                Just My .02
                               Good Luck!!!!

OPI 

[buckiryder]

Had a similar sound on my '72 a while back. Turns out a high frequency vibe was causing the gas tank to barely contact the backbone of the frame. Drove me crazy trying to find out what the noise was. Found it by pressing on the tank with one hand as I rode. I put a piece of old inner tube between the tank and backbone and the noise was gone!