Running poorly. Is it electrics or carbs or both?

[Charliecharlcomb]

Hi there. My CB500 hasn't been used much over the last 6 years, being stored for two long periods of 3 and 2 years. This time it started reasonably easily with its new battery but ran like a dog. I've removed the carbs (inside the float bowl for cylinder 3 was dry and all fluffy) and replaced the O rings for the main jets and float seals which were perished. Everything else looks good and unblocked. Having ridden it several times since then it has rarely run properly. Either refusing to rev at all (but better after carb clean) to only running on 2 cylinders (2 and 3) to going just great. It has only done 7,500 miles in the last 20 years after a major rebuild and so isn't worn in any way, just chronically underused.
Having suspected the carbs and fuel supply (there were flakes of rust in the tank) having rectified that side of things the problem persists. I'm beginning to think it is a combination of things. I've replaced the plugs and caps (again better but not fixed), will investigate possible dry connections to the coil, and would like to get the carbs balanced and jets correctly adjusted, but can't do when it is running like it is at the moment. The fuel tap seemed to only feed fuel through one of the two pipes and now drips when off so I'm replacing that as a washer change didn't fix it.
It's been really puzzling and frustrating. I'm thinking of replacing the coils next (and would prefer not to go for electronic ignition). Any ideas as I'd love to start using this beautiful machine properly again?

[K2-K6]

It looks like a combination of the two as you suspect.

That bit about running on 2 and 3 cylinders is common to one side of ignition system not reliably sparking as they are separated for those two and successively 1 and 4.
Coils on these are generally very reliable so wouldnt be prime suspect.  It's worth going through points and the small insulation washers where the wire connects to them, then making sure the wires to coils from there are connected with decent continuity before judging the HT section. That may bring up something, and of course points gap / timing.

Carbs you can synchronise mechanically as a reliable method not dependent on running to give you baseline in that respect http://www.sohc.co.uk/index.php/topic,17769.0.html will get you plenty accurate enough to take that concern out of the equation.

When they've been sitting a while you can chase carb cleaning through a number of times before you get them sufficiently and reliably clear enough to run competently. 

One method of carb diagnosis is if a cylinder is not obviously running, then remove the synch screw and spray carb cleaner in there with a tube.  If it chimes in with that it indicates a jet blockage.  May help you seperate the cause as no response points to ignition.

[Bryanj]

Clean an reset the points plus make sure pivot isnt sticking, grease gets very hard over time

[paulbaker1954]

You can always swap the coils over to see if the problem moves to 1 and 4

In fact I think you can swap by just moving wires, switch the yellow and blue wires over that feed the coils and also swap the HT leads. Be good for another member to confirm this method.

[jon stead]

You can always swap the coils over to see if the problem moves to 1 and 4

In fact I think you can swap by just moving wires, switch the yellow and blue wires over that feed the coils and also swap the HT leads. Be good for another member to confirm this method.

Yes that would work.

From memory, blue fed coil does 2 and 3 and yellow fed coil does 1 and 4

[paulbaker1954]

You can always swap the coils over to see if the problem moves to 1 and 4

In fact I think you can swap by just moving wires, switch the yellow and blue wires over that feed the coils and also swap the HT leads. Be good for another member to confirm this method.

Yes that would work.

From memory, blue fed coil does 2 and 3 and yellow fed coil does 1 and 4

Actually other way round according to wiring diagram yellow feeds 2 and 3 and blue 1 and 4