I've had 2 problems recently and managed to fix both, the 'bird is running sweetly (as it should), just adding the info here in case it helps anyone else searching for similar faults.
Bike is a 97 Blackbird CRBXX1100 - 97 model has carbs, not FI.
Push start button, a kind of fizz/pop is heard, lights go out, dash lights go out, clock goes out, bike is dead.
Push start works, but it really sounds bad and only just idles with loud knocking noises and the tiniest bit of gas/throttle and it stalls and dies.
Meter across the batt measures 12.3V but drops to 0v when the start is pushed.
Problem is the batt has failed internally and needed replacing. Thought it might be the dreaded Rect/Reg problem but was just the battery. New battery has it running fine again.
Bike runs a bit rough when cold but better when warmed up.
Next morning is hard to start, runs rough, gets a bit better then stalls.
Will start again, but stalls when given some throttle.
Tried starting again but nothing. Cranks over just fine, but won't fire.
Problem is no fuel, not getting fuel because the vacuum hose on the back of the fuel tap has slipped off. The hose must have been working its way off slowly causing it to run rough at first, then die all together when it finally came all the way off.
Lifted the tank, removed the fuel lines from the back of the carbs, put them in a container and cranked the bike over - nothing, not getting any fuel ...bugger!!
Just about to completely remove the tank and start on checking the tap and diaphram, fuel pump, see if anything is blocked then I notice a small connection on the back of the tap that looks like it should have a hose attached to it. Find the vacuum hose laying across the back of the engine connected to nothing, reconnect it to the tank, crank the engine and out comes plenty of fuel into the container - Yay!!
Connect everything back up and she fires first go.
I'm not overly mechanically inclined but still managed to work my through these faults and fix them myself with a minimum of time and effort, and most importantly, minimum cost! So even if you're a complete mechanical numpty, it's still worth taking a look at the basics before setting off to the local bike shop.
Hope that helps someone if they search for a similar fault