[FrankenDesmo]

Originally Posted by Mr Gazza

The carb heater tap is a diverter valve, that is to say it always supplies the oil cooler in which ever orientation. As a general rule ball valves always have the handle pointing to the direction of flow. So yours is currently to the oil cooler only, when the handle points up the carb heater line, then the flow will go to the carbs and also the cooler.

That's what I thought was happening, cheers for the confirmation.

The sort of weather we're having at the moment might initiate carb icing; cool but humid, so it wouldn't be a bad idea to have the warmers turned on. It also helps no end to blank off the air to the cooler with a wrap round affair of some sort. It will not overheat until the air temps get well on their way to the 20's.

I'll keep that in mind particularly as I'm right up north.

I think it is definitely worth your while trying it again with the vacuum hole blanked and new spark plugs, before you wrench the carbs off. Also check the throttle and choke cables for free play, either could be holding the butterflies open if they are out of adjustment and upsetting the tickover.
It would be rather frustrating to find nothing wrong with the carbs after going to the trouble of removing and stripping them, not to mention the expense and wait for diaphragms ect… That's not to say that you don't have a carb problem, but I personally would try all the cheap and easy things first.

I suppose I was slightly worried that further trial runs could lead to permanent damage on the top cylinder, as well as not being sure that the carbs have been in a great state the whole time I've owned it - I really only got a few days riding before it was SORN'd due to the RR issue, and it did have the odd hesitation down low (though that could all be due to the scottoiler vacuum line coming loose).

I've actually got them off bar the throttle cables - tomorrow I'll check the cable adjustment, have a look for any potential vacuum leaks, and throw in the new plugs & air filter. It's involved but not particularly onerous to get the carbs off if I find I need to after that. One task that is much less daunting now that I've actually done it.

Originally Posted by Darren69

I'd go with Gary's suggestion as its a real pain getting them off.I'd put a good dose of fuel injector cleaner in the fuel and running it through and maybe spray carb cleaner in if the injector cleaner isn't helping. I suspect that the vacuum pipe was probably leaking too which won't help.

I suppose it can't hurt to try! I'll pick up some easy start & injector cleaner while I'm out and about.