Yep. I agree with that and it now has new insulating spacers on both sides – but no change. I’ve checked the chokes, both okay, next I’m borrowing vacuum guages from a mate either today or tomorrow.
I’m baffled. When it’s warmed up, when I blip the throttle the engine sticks at about 3000rpm. I then press the engine “stop” button, restart the engine without touching the throttle and the engine ticks over okay. Repeat with the same result. Obviously looks like sticking slides. However, if the slides stick open, there would be some free play in the throttle cables, and there is none.
I’m clutching at straws now. When I have the vacuum guages I’m going to set the carbs up from scratch and if there’s no change I’ll have to bite the bullet and pay someone who knows what he’s doing. Regards. Dave
The throttle cables must have a bit of free play. Make sure you can lift the cables out of the carb top adjusters a tiny bit when the throttle is released. A cople of mm is enough.
The tickover is then set using the knurled screws in the side of the carbs.
How have you got the air screws adjusted? These are the smaller screws just above the float bowl, they should be about 1 & 1/2 to 2 turns out.
Balancing of the carbs isn’t that critical, I do mine by ear listening to the clicks as the throttle shuts (after winding the throttle stop screws out)
Take a bow, Don-Spada. You’ve given me a metaphorical slap and woken me up.
I had synchronised the throttle slides by ear. No problem, except that I hadn’t wound out the throttle stop screws beforehand! Stupid mistake. I do realise that the slides dont need to lift much to get the engine to about 3000rpm.
I did say I was missing something obvious and as soon as I read your reply there it was. So, thank you Don. I’ll now go and stand in the naughty corner for an hour!
Glad you have got it sorted. 
Yes, that’s what matters. Thank you to everybody who offered advice
Regards. Dave
Air leak…spray brake cleaner around all the inlet tract, if the engine speeds up or makes a different note then you have a rubber or gasket gone.
I didn’t know that one but two new insulation spacers fitted now. Regards. Dave