Ignition fure blows after a while

Hello,
I picked up a nice 82 CSR1000 with 2,550 miles on it! It was running fine until recently, now the ignition fuse blows after it runs 5 minutes or so, sometimes longer. Everything is stock as far as I know. I haven't torn anything apart yet because I'm really busy with a building project right now and I just don't have time. A friend said he had an older LTD1000 and had to replace the coils because they shorted when they warmed up. It sounds feasible because the fuse doesn't blow right away so the time delay indicates a high draw but not a short. (I've been an EE tech for 25 yrs so I have some experience how things like this work).
Anyone had similar problems?
thanks Guys!

I had the same problem on my '78 Z1-R and someone on this site was kind enough to point out the problem. In my case, the fuse connections needed cleaned. They looked totally clean but were really oxidized and building resistance. The fuse and wire would get hot and blow. Once I cleaned them with some scotchbrite the fuse never blew again.

Are your fuses buss-type of the newer blade-style??

Hey, I'm willing to try anything. As I said, I bought the bike with 2,550 mile and it had sat for years collecting dust (and maybe corrosion). They are the older short round glass tube type, hard to find exact replacements but Advance auto had ones close enough, at least the length was right.I have a current probe for use with a multimeter. I should be able to see how much current it draws and if it's higher than the fuse rating. I guess I could just pull the fuse and connect the meter leads across the fuse clips and read directly.
Thanks for the tip, I wouldn't have thought of that.

I FOUND IT!!!
I didn't think it was possible but there is some sort of short in the main harness under the tank. I traced it out by using my own current limited power supply. I hooked the PS up to the output of the blown fuse and ground. I started the bike and could see about 2 amps while it was running, then suddenly 0 volts out, max current and the engine stalled. I started wiggling wires and removed the tank and found that it's in the bundled harness under the tank. Who'd a thunk it? I haven't cut the harness open to see exactly what's wrong but it's gotta be either a melted wire (BAD!) or just a separated connector or short of some type. That's easy to fix, if it's melted then I have to figure out why so it doesn't happen again.
Thanks for your help and suggestions.

Problem solved and riding again! It was a short to the staked in nut for the left side coil bracket. The coil wire for the right coil exited the bundle sort of on the lower left side of the harness and was wrapped over the top of the main harness bundle. That bend had been riding on the sharp edge of the nut and wore through. All is well!
Thanks again!

Gotta luv those current-limited supplies! Nice job.