Drum brake clunk?

So my bro in law rode with me on my first legal ride on real (non 25mph subdivision) roads since I got my permit a week and a half ago. His goal was to get me going over 50mph a few times so I could see what it feels like and get my confidence up. Well it worked! One thing I did notice is that over 40mph or so when I apply the rear drum brake there's a distinct clunk and you can feel it in the bike. Kind of like the feeling when you've hit 1st gear downshifting for a stop, only from the back of the bike. I doesn't happen a lower speeds, doesn't seem to effect the braking, and there's still plenty of space in the "usable" zone. I checked the service manual and it doesn't look like there's much in the braking mechanism that'd do that. I did some Internet searches but didn't turn up anything. It's not presently causing problems, just doesn't seem right. Any thoughts or suggestions?

I'd remove the rear wheel & inspect the brake shoes as some of the Kawasaki's are experiancing glue failure due to age of the adhesive. One forum member here(Martin CSR?) had his rear wheel lock up, fortunately at low speed when his brake shoes jammed.

And would also assure the rear axle is properly aligned in the swing arm, adjusters are tight on both sides, and that the axle nut is tight.

And that the brake torque arm is tightened at both ends.

Also assure the shocks are undamaged and snug on their mounts.

Good Fortune!

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I wouldn't ride it again till you get it sorted out.
Also check the swing arm pivot bearings/ bushings and bolt. Something is wrong and the clunk, is a polite way of your bike saying I need some Luv.

Patton wrote: And would also assure the rear axle is properly aligned in the swing arm, adjusters are tight on both sides, and that the axle nut is tight.

And that the brake torque arm is tightened at both ends.

Also assure the shocks are undamaged and snug on their mounts.

Good Fortune!

Thanks all for the suggestions! Looks like Patton got it. Checking out the axle nut it looks like I didn't torque it down enough and it's slipping 1/16th-1/8th of an inch in its bracket. I think that may be the culprit. I'm hopefully having my new tires put on tomorrow so I'll pay special attention to that during reassembly. I'll also pull open the brake just to double check but I think I found the source.