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

[billdn]

Aarrgh! 🙃 thought it was had to screw the bejesus out of adjuster to get slide down . 🤣😉

[Bryanj]

In my defence comf's was the first set of 400 i have had where just about every screw possible was undone and i must give thanks to Nurse Julie and Oddjob for helping out with parts and once again appologies for the wrong instructions.
Iwould now suggest that on the 400 wind out the tickover screw, make sure that the choke lever is NOT touching the fast idle cam then starting with all the screw adjusters removed and nuts, links, washers etc removed screw down one adjuster keepin a close eye on the arm the big tickover screw pushes on till it just moves then back off 1/2 to 1 turn(i.e.screw up) then do same to each adjuster in turn.
Now fit washers, links and nuts as removed making sure the adjuster doesnt move as you fit the nut on each one.
Now fit the idle screw and screw in until your tiny drill shank just fits under the engine side of the slide on the slide with biggest gap and adjust the othe slides to that one.
This should give a good starting settup with all slides down.

[Cappodimonte]

If you want a really in depth description of Stripping/Rebuilding Carbs which covers  everything you need to know, have a look at ‘THE VINTAGE BIKE BUILDER’.
It’s an American site but one of the best I have encountered, having plenty of pictures to back up the written word so you shouldn’t get lost in the information.

[Laverdaroo]

Or look at Classic Octane, he takes a set of 400 and 500 carbs to bits and rebuilds them fromscratch. MASSIVE HELP!!!

[McCabe-Thiele (Ted)]

I used this U-tube video - there is plenty of stuuf out there if you are a first timer like I was.://www.youtube.com/watch?v=JFTOfYl5BSc

.https://www.youtube.com/watch?v=JFTOfYl5BSc

[Laverdaroo]

Thats the chap.


I am TAYLOR!

[billdn]

Sorry to return to this but still having problems!
I watched the videos mentioned and even carefully read the Vintage Biker piece on setting up the carbs- no joy still won't idle.
I've tried BryanJ's revised carb set up still no joy.
It just won't return to idle speed of 1200rpm. rev it to 2000rpm and won't drop, rev it to 300rpm drops to 2000, rev it to 4000 drops to 3000rpm. I've disconnected cables and it still won't drop, so can't be cables! and revved by hand.
I've adjusted air mixture screws to 1 1/2 turns out and nothing.
But again, press the top of the brass nuts on top of the sliders and you can get the revs to drop but then drops too low and stalls. it can be reduced by adjusting idle screw but continually doing that is not right, obviously!
Is it possible I've reassembled wrongly the sliders but they to be smooth enough in their action?
Is it possible to get the main spring the wrong way round but don't see how, it closes the carbs with a quick action?
Frustrated of Sussex

[Oddjob]

How far down have they been dismantled? Sounds like a lifter arm problem, maybe one of the internal springs is missing or corroded to the extent it’s not pushing the arm down enough when it’s lifted. The fact pushing down on the top nut reduces the revs would make me suspect this.

[McCabe-Thiele (Ted)]

If pressing the brass nut down drops the revs then I suspect you have something not assembled correctly  in the slider mechanism / links. There is a spring as well as the ball cups either side. Did you remove the lever bolted to the slider top that has the locking tab?
Even though the throttle return spring is quite strong the lever mechanism has to be working freely via the links to shut off effectively at all temperatures.

You have three links with spring & cups on each carb. One attached to the slider inside plus two external ones on the alloy body with the plastic cross links. If just one of the four sets of three links is not assembled correctly it could explain your issue. Twelve links in total that need checking.
Another thought have you removed the fast idle cam & lost the little ball bearing?

Update:- looks like my reply duplicates Kens thoughts.

[billdn]

Cheers Ted and Oddjob,
Have stripped down and cleaned slider assembly, lubed etc and reassembled.  Couldn't really see much wrong, no major debris and everything in the right place , thankfully. Did notice that the 2 springs in the slider arm although are same length were slightly different colours, so swapped them around , TTYL anything now.
Ted, still have little ball bearing in choke mechanism too.
Odd job, was full strip , everything apart including slider arm ..

[McCabe-Thiele (Ted)]

I'm trying to remember but I think one of the adjusters is quite critical if you overtighten it - I think it's the one in the slider itself. Mine was marked with yellow paint.

[billdn]

Don't recall reading that Ted  isn't that on the 500 or 550, hope so as all mine have yellow paint on 🤣

[McCabe-Thiele (Ted)]

Don't recall reading that Ted  isn't that on the 500 or 550, hope so as all mine have yellow paint on 🤣

I did my best to return all the lock nuts to their original position on my 400 carb rebuild. I seem to recall that on one slider all the paint fell off so I had to fiddle with it a tad to make it return freely.

All 4 of my carb sliders were stuck solid. It took me several days of soaking the carbs in Petrol & other solvents before I freed them off.
It was a slow process as there was nowhere I could safely lever against to free them off.
It's anecdotal experience not anything I read. Looking at my post it reads as though it's down to one adjuster - bad phrasing - I meant the slider ones seem more critical than the external ones imho.

[Oddjob]

Were all the little black rods fitted Bill, they slide inside the springs and are cupped on the ends to match the ball on the lifter arm. If those are missing the spring pressure would be reduced and allow it to remain raised.

There should be 3 in each lifter arm fitting.

https://images.cmsnl.com/img/partslists/honda-cb400f-england-engine-group-1j-1k-2j-2k_bigma000080e01-4_c702.gif

You can see them in number 96 grouping.

[billdn]

Yep they're all there but one T cup bit in lower end of riser ( one on which brass cap fits) doesn't want to come out and didn't during strip down .