battery voltage drop and backfiring

Have a 1978 KZ 1000 LTD. Have two issues I have been chasing; battery power loss and backfiring

After about 30 miles, the battery will loose power to the point that the turn signals won't work; power dropped from 12.26 to 11.89 on last ride. Other times the battery voltage has dropped to 8+ volts.

I have spent considerable time on the phone with a shop in Chicago and with a friend (he lives four hours away) going through tests on the alternator, rectifier, and regulator; all test good.

Previous owner has changed ignition to a Dyna set up. Test the pick up coils and coils. Everything seems to be performing well with the ignition system.

Have replaced battery and positive battery cable. I have cleaned the wire ends on the negative battery cable and will most likely change this next.

Any help will be most appreciated. :S

Thanks

Sounds like your going in the right direction to me. I would have checked the generator (alternator) first, changed battery, changed cables, then proceeded with the rest.

You have 3 wires coming from Your alternator...have You tested all 3 of those wires to make sure that one of them is not broken,or breaking?(weakening)
These wires will run from the alt.cover,and in behind the front sprocket cover(clutch cover),so You might have to remove that cover to follow the routing of them.And they will be cased in a loom,and will connect to the panel under Your seat,where all of the wiring is hooked up.This might be different on Your bike(Mine is a 77 KZ1000),but You will still have the 3 wires coming from the alternator(dynamo)
I had the same symptoms a lot of years ago on my bike,and it turned out to be just that.My fully charged(brand new) battery would slowly drain and the bike would eventually die.
Have You tested the alternator,to see what kind of voltage it's putting out to the battery?
You want to check this with the engine running,and put Your test-leads onto the battery terminals.You should be getting over 13 volts with the engine running.
When I was having this problem,a Friend of Mine tested the 3 wires coming from the alternator(I didn't know a whole lot about it back then,but I've sure learned SINCE then,lol),and it was determined from the low voltage,that I had either a loose connection,or a broken wire.We pulled the alternator cover off to find one of the 3 wires,was in fact completely broken...
So start there and let Us know what Your test results are,as far as what voltage You're getting from the alternator...good luck,Bud.