Ideas on how valves got this loose?

I'm currently fixing up a very very hard starting 83 kz750F. It has 30k miles on it and I've ridden probably around 5 miles while messing with the carbs. Most of the valves were extremely tight to the point where on exhaust and intake of cyl 1 and exhaust of cylinder 2 I couldn't even fit the .038mm feeler. Only intake valve of cylinder 2 was within spec. Oddly, exhaust valves of 3 and 4 were WAY loose and intake 4 was just very loose. It is my understanding that these shim under bucket valves are supposed to tighten with wear.

My first thought was that someone had mixed up what shims they were putting in on a previous valve job but when I took out the shims in the bike to replace with new ones they are all of similar size. Exhaust shims from cyl 1-4 was as follows: 2.45mm, 2.4mm, 2.4mm, 2.4mm. Intake shims from cyl 1-4: 2.45, 2.4, 2.3, 2.45.

I put new shims in and now all the valves are within spec except for exhaust 3 and 4 because I thought maybe I was somehow measuring wrong so I was conservative in bumping up the sizes on them.

The new shim sizes are:

exhaust 1-4, 2.30, 2.25, 2.60, 2.50
intake    1-4, 2.30, 2.40, 2.20, 2.55

but it looks like I'm going to have to bump exhaust 3 and 4 to 2.85 and 2.80

What gives? Am I overthinking this or is there something else going on here?

Just a thought...

If the valves had no clearance that means the valves were hanging open and building up carbon on the sealing surfaces.  Changing the shims will get back clearance, and after running the carbon will be cleared off thus further increasing clearance.  

Thanks, that's the only thing I've heard that could make any sense. Well, I've replace the regulator and IC igniter and rewired some broken wires so it looks like all the electrical system is working fine now. It looks like I'm still not getting any gas from the carbs even with the float bowls filled to the right height. She'll start right up if I drop some gas into a cylinder but it can't seem to suck in anymore fuel to keep going. 

If I can get it running then I'll recheck the valve clearances after a couple hundred miles and if anythings changed I'll pull the head.