Bike not starting /:

I have a 1980 GS550L which I bought a while ago and started work modifying it to make it into a bobber. It always ran well, started well (except on cold mornings). But the other day I was riding to work and it starting missing and losing power, so I dropped a gear and went full throttle, which did nothing, so I pulled out the choke, dropped a gear and again, went full throttle. Still did nothing and then started losing more power and then died completely. Sounded like it was running out of fuel but I had heaps in the tank. I pulled over and started cranking it, but it wouldn't start at all. Then I pushed it down a hill to try push start it, it started then died instantly. So I got towed home.
I assumed it was a fuel problem so I drained the carbys, but that didn't help. So I took the tank off and checked the fuel filter which didn't look flash, so I bought a new one and gave the tank a thorough clean out. Reassembled it and still nothing.
Checked the spark and its not flash but its enough to start the bike because it's no worse than it was when I got it. Really need this bike running again because my partner just sold her car and was going to use mine til she gets another one - I was gonna take the bike to work.

Any help would be really appreciated, I'm kind of at a loss now. Also checked compression which seems fine. The bike doesn't cough or anything that would indicate its trying to start. Really weird.

a couple quick thoughts, coil and points

I think coils are alright since it has spark? I'm pretty sure it doesn't have points but will have to double check that.
And yeah fuel runs freely through the petcock

The coil can be bad and still produce a lil spark. You need a strong spark, blue in color and it should make a snapping noise. If you can barley see the spark, yer coil is prolly shot. try swapping with another one to test it.
Make all the wire connections on the ignition circuit are good.

Sweet cheers. I'll look into new coils.

If your bike has twin coils, 1 per cylinder, unless you are EXTREMELY unlucky, I can't see 2 coils burning out at once. You can test for fuel problems by with either starting spray or just by squirting gas into the carb. Be careful if you use gas its easy to ignite with a back fire. If its not a gas issue, I'd be looking for some kind of wiring problem.
Let us know what you find out

Good Luck.....Mike

Hey there yeah I had a look earlier and it is twin coils (one for two cylinders, its for cyl) so am starting to doubt thats the case, but am going to get them tested first. Its not gas as i did spray some stuff in there and it wouldn't even cough or try to start so starting to think it might be electrical, which will be annoying as I hate electrical **** haha. Thinking the bike needs a strip down and complete rebuild anyway but would like to know its gonna start afterwards.