The combination you are suggesting mortifies me. It would help to know what the tow vehicle is. Hitch limitations need to be considered. Class III hitches have a 500 pound tongue weight capacity.....the amount of weight the hitch [and its connections to the tow vehicle] are designed to withstand, allowing for safe handling of what ever you may encounter on the road. The KLR will eat up 400 pounds [+-] of that limitation, add the weight of the carrier and the scooter.....
....and your looking at a Class IV or V hitch to withstand the weight. Now figure out how to add a trailer hitch to the back of the motorcycle carrier that will be adequate for the pop-up camper. And how is all this tongue weight affecting the handling of the tow vehicle? Weight at the rear bumper is taking weight off the front axle. Life gets exciting when the trailer starts fishtailing, and your front end is not responding, because it's too light in the front. And like our bikes, braking is most effective in the front of the tow vehicle, and that will be compromised. A blown tire anywhere in this equation at 50 MPH would be interesting at best, fatal at the worst.
Weight-distributing attachments might be an option. These slide into a Class 3/4/5 weight carrying receiver hitches, and redistributes hitch tongue weight. Weight distributing hitches are normally used for heavier trailers up to 10,000 lbs. Usually 2 spring bars, one on each side of the trailer to lift up and apply leverage to the tow vehicle, thereby redistributing tongue weight from the rear axle to the front. This provides more vehicle stability while towing. Weight distributing hitches currently come in two configurations: One with square bars that hook to the center of the ball mount, called trunnion bars, and one with round bars that slide into the bottom of the ball mount, called round bars.
Anything is possible with enough resources, mostly green in color, with pictures of Ben Franklin on them.
I've seen this set up doubled up and work well on a Class C motor home:
Sorry to sound pessimistic. You may well have a E or F-450 or equivalent or bigger, and my fear mongering would all for naught. If you have anything less than that for a tow vehicle, please consider my concerns. And don't forget to check the load rating on your tow vehicle tires.