my 109 1983 x mod ffr recently failed its test on co emissions (10%+ CO )
the hc emissions are fine (850). Ive put on a new exhaust manifold, as the old one was cracked . i put on a new brit part carb as i thought the old one was worn and hence high emissions. All new gaskets fited. Only old bit is the solonoid.
could the solonid be causing high emisions?
does any one know where to get a new(24v ) one from? part number ect

Is this the solenoid that shuts down the idle circuit on power-off to prevent dieseling? No, this will not cause high emissions.

Were I you I'd have taken a more systematic look at the problem. TBH this could simply have been an adjustment - if this was at idle Id've checked the mixture setting of the carburettor. if tthe carb is a Zeenith it could also have had a warped cover causing a rich mix - but that should have shown up in the HC count.
Alan

I don't think it will be the solenoid. It sounds like it is set up way too rich. This can be an over fuel, a blockage somewhere, a dirty air filter or the choke stuck on. I glanced at mine in the test today and I think it was 148ppm HC and 1.5% CO and its set just to the rich side on idle (14.1 AFR). You need to ensure that your engine is properly warmed up when they do the test. What carb is it? Solex, Zenith, Weber 34, Weber 32/34?

Hyrdocarbons (HC's) are unburnt fuel, high HC's are usually a result of either a to weak fuel mixture or incorrect ignition timing (usually to advanced), it can also be a sign of a worn engine burning oil. I will also add that ignition timing does not have much of an effect on CO. I would say you are over fuelling, you need to weaken your carb fuel mixture, ideally you want about 3.5 to 4% CO and that should (given correct ignition timing) produce about 800 ish ppm HC's on a good engine.