Curvy Ignition fault?

Took a gamble as you do, bought a 2000 curvy of a mate of a mate, non runner to restore for the wife.
Back home charged battery, fresh fuel fired up! but running rough, stripped carbs nothing blocked, no dirt. Constant Misfire / back fire seemed to be on the rear cylinder swapped out the coils , new plugs, leads etc fault remained at the rear cylinder. compression tested, 155psi and even across both cylinders wet & dry, it has done 40k miles.Valve clearances ok. Wiring loom check out for dodgy plugs and rubbing through anywhere.
I am now thinking CDI or signal generator, has anyone had a similar fault ?
Would a faulty signal generator just affect one cylinder?
Anyone got a spare CDI and signal generator i could borrow, or very cheap??
Thanks in advance.

[Biker Biggles]

Had something similar.Turned out to be chafed wiring loom under the rider seat.Found it by checking continuity of the wires that go between the coils and the cdi unit under the tail section.The loom chafes where the seat bolts protrude and further back where it does a sharp turn around the subframe under the pillion seat.

[Sid Squid]

Originally Posted by matty450

Would a faulty signal generator just affect one cylinder?

No.

Originally Posted by matty450

Anyone got a spare CDI and signal generator i could borrow, or very cheap?

CDI won't help - SV doesn't have CDI. Academic? Perhaps, but if you're looking for an ignition fault it helps to know precisely what sort of system you're dealing with.

Ignition fault is a possibility of course, and a wiring fault is definitely worth looking for.
Despite the cleaning you've done, a carbed SV left unused for a long period gums up the small drillings in the pilot circuit and causes a persistent weak mixture late burn.

Originally Posted by Sid Squid

No.
CDI won't help - SV doesn't have CDI. Academic? Perhaps, but if you're looking for an ignition fault it helps to know precisely what sort of system you're dealing with.

Ignition fault is a possibility of course, and a wiring fault is definitely worth looking for.
Despite the cleaning you've done, a carbed SV left unused for a long period gums up the small drillings in the pilot circuit and causes a persistent weak mixture late burn.

ECU then, box under in the tail unit. Will double check the pilot circuits, and loom.

[embee]

.........anyone else?......no?......Ok, might as well be me then.

Double check the choke plungers are closing properly. I know you've stripped the carbs, but it's such a common issue with corrosion in the springs/plungers/cables that it's got to be worth a second look. They only have to be cracked off the seats a fraction to mess up the slow running.

[mikerj]

Originally Posted by Sid Squid

Despite the cleaning you've done, a carbed SV left unused for a long period gums up the small drillings in the pilot circuit and causes a persistent weak mixture late burn.

Agreed, much more likely a carb problem given that changing the ignition components most likely to cause this hasn't made any difference.