More carb troubles, engine won't return to idle revs

[billdn]

The saga continues. I've refitted carbs after setting sliders using BrianJ's method, and others and seemed to achieve what was required.  Bike starts fine and when warm ease off choke and all ok. But when revved up to say 3000rpm the throttles close properly on handlebars, but revs do not drop back to tickover 1200rpm. This can be achieved by using main idle screw, but when revved again the same happens meaning using idle screw again - could make for interesting riding! When revved higher say 4000rpm still won't drop back past 2000 without using idle screw.
I have fitted main air box to back of carbs but not yet connected up to filter box (suspected I'd be taking them off again!) and air filter not fitted but this shouldn't make any difference at this stage I believe. Carbs have been stripped/cleaned and replaced brass float rods and carb float height set.
Any ideas? Anyone? Please !

[Nurse Julie]

Is the throttle cable lock nut thingy done up properly Bill? (I'm trying to remember the proper name for it...... But 🤔🤔🤔) It's the bit where the cable sits in a bracket and you lock the nut to stop the cable moving.

[billdn]

The one on the open/ close butterfly thing or the handlebar ?

[Nurse Julie]

The one on the open/ close butterfly thing or the handlebar ?

On the butterfly Bill.

[billdn]

I'll double check but everything seems to open/  close OK but you never know bit fiddly at that bit .

[McCabe-Thiele (Ted)]

Reads like the throttle closing cable is not working as it should at the carb end - I made sure there was some slack in the cable so it closed off fully.
Could it be the heat of the engine is making the cables bind?

[Bryanj]

Does sound like closing cable to me as well, if you twist the throttle the wrong way(forwards) after you let the throttle go do the revs come down, there is a spring loaded bit on the operating mechanism

[Oddjob]

Try disconnecting the cables completely. Rev the engine using the butterfly by hand and see if it still does it. You'll need a remote fuel supply to do it though.

[billdn]

Does sound like closing cable to me as well, if you twist the throttle the wrong way(forwards) after you let the throttle go do the revs come down, there is a spring loaded bit on the operating mechanism

Thanks Bryan , did think that too but doesn't make any difference.  Also adjusted both cables but made little difference.  Also made sure choke screw was not operating choke.
Incidentally though as I was pushing/ prodding stuff I did note that if I pressed on brass caps on sliders on 1 and 2 carbs revs did settle, almost if not quite returning down after operating. 

[billdn]

Try disconnecting the cables completely. Rev the engine using the butterfly by hand and see if it still does it. You'll need a remote fuel supply to do it though.

You don't like me do you 🤣
Worth a punt though. Given up Haynes manual (sorry Bryan) reference to 56mm distance on closing throttle to end .

[billdn]

Try disconnecting the cables completely. Rev the engine using the butterfly by hand and see if it still does it. You'll need a remote fuel supply to do it though.

You don't like me do you 🤣
Worth a punt though. Given up Haynes manual (sorry Bryan) reference to 56mm distance on closing throttle to end .

Interesting, cables disconnected but still same issue and  again could be resolved by pressing on top of sliders on 1 and 2 carbs.
Not quite sure what's incorrectly aligned but must be something of that sort 🤔
Carbs off again !

[McCabe-Thiele (Ted)]

Incidentally though as I was pushing/ prodding stuff I did note that if I pressed on brass caps on sliders on 1 and 2 carbs revs did settle, almost if not quite returning down after operating.
[/quote]
That sounds like you have found the problem  area.
Have you overhauled the carbs previously ?

[billdn]

No, this first time off since I've had bike, only did it as waiting for rebore etc. And thought ideal time , any ideas Ted?

[McCabe-Thiele (Ted)]

Mine were seized up solid when I bought my 400. I had to soak the carb bodies in a series of solvents - Petrol, Acetone & ,carb cleaning spray to get them to move a mm. I suspect you just need to clean the sliders up properly by removing them fully - you could remove the slider top caps & use some carb cleaning spray if a full dismantle is too difficult or inconvenient.
There is a spring loaded mechanism that has ball cups at each end that can gum up as well.

[Bryanj]

Just rebuilt comfysofas carbs and noticed that on the 400 set i had to start the bench sync with the adjusters screwed up a bit or the idle screw lever would not touch the bracket and the choke did not operate the high idle lever.
My instruction were written for the 500 carbs which dont have thehigh idle so that could be a problem, sorry