KZ1300 carb kits... help?

You might just have a stuck ring. Get your self a can of "Mopar Combustion Chamber cleaner" Part #04318001AB at any Mopar dealer. Do not let yourself get talked into any other "stuff" this is by far the best and quickest working. Start the engine and let it heat up. Remove the suspect spark plug and spray into the cylinder about a 3-4 second burst than immediately replace the spark plug. Allow to sit for about an hour and repeat the process about 4-5 times. After the first application rev the engine a bunch of times or take it for a brisk ride until the engine is at full temperature. If the ring or rings are stuck, this should free them up. You may also have an improperly adjusted valve at that cylinder which is staying open by only a Thou of an inch or so. this will also be sealed with your oil treatment. You may also have a slightly bent valve.

I have two of these things and pulling the top end off of this thing is a pain in the ASS (quite time consuming) I would do my best to determine what the problem exactly was before you tare into it.

If valve gap adjustment doesn't bring compression to cyl #5, would perform leakdown test to determine where compression is escaping.

Good Luck!