Topic: some idling trouble

[Burnboy]

This is on my 350f but should be a general question. My bike will only start with the choke all the way on (pushed down). It will idle ok, not great, the main idle screw is turned all the way in. If I give it some gas will rev fine till about mid range but that's it, once I let go of the throttle the revs drop and the bike dies. Also if I pull the choke back up the bike will die. Everything is stock. New plugs, timing is fine, lash is fine. It seems like it is not getting enough gas I guess. Any suggestions? Im going to play with the idle air screws next.

[Gordon]

Let's clarify the choke position first.  I don't remember for sure on the 350, but choke lever in the up position is typically when the choke is closed, which is where it will normally need to be to start a cold engine.  Pushing it down opens it for regular, warmed-up engine running. 

[Burnboy]

The lever has a down arrow and says on.

Idle air screws are now 2.5 turns out, they are on the carb side. Bike only revs till about 3700 on full throttle.

Also I pulled the plugs and they are pretty sooty

[Inigo Montoya]

Are the idle jets on the carbs clean? Sooty would indicate a very rich condition. you might be leaving the choke on too much after start up.

[Burnboy]

After reading more it does seem as if Im rich.

as soon as I turn the choke off it dies

[Inigo Montoya]

That usually indicates that either the idle circuit is plugged up or there is was too much air coming in. The choke provides the additional vacuum to pull from the mains I am guessing.

[Gordon]

After reading more it does seem as if Im rich.

as soon as I turn the choke off it dies

Forgive me for harping on this one thing, but it's an important one.  I think there's still some confusion as to when the choke is open and closed.  If the bike is running rich and you open (turn off) the choke it would run better, because it would be getting more air and less fuel.  

[flybox1]

for normal running, once warm, the choke lever should be pressed down.
if your idle screw is all the way in, you've probably bench synched them fully closed.
re-bench synch with 1/8" drill bit, with the idle screw touching the tang +1 turn IN(increasing the idle).
AF screws should be .75 turns out +/-
floats at 24mm's

tell us what you did to your carbs?
needle position? float height?
emulsion tubes and jets squeaky clean?
slides in backwards?

[Burnboy]

Just took off the filter to confirm, pushing down on choke (choke on according to lever) opens the butterfly valve, thus leaning things out(more air).

So the bike needs more air, therefore it is rich. If I turn off the choke (pull lever up, closing butterfly valve) it gets less air and dies.

So turning in the air screw will lean the mixture which is what I want correct?

Does the symptom of it not wanting to rev past 4 grand come from it being too rich as well?

[flybox1]

Maybe...
more info needed.
what exhaust do you have?
stock airbox? new filter?
stock main jet(75)?

small changes with carbs on these 350F's make big differences.
ensure everything is clean, and your floats are at 24mms so you're not drowning your main jets.
AF screws are usually ~1turn out.

when warm and running, your choke lever should be pressed down, and idle screw adjusted to get it to idle around 1300-1500

[Burnboy]

Stock 4 into 2 exhaust.
Stock airbox, just removed air box and bike still wont start without the choke on(butterfly valves opened.) Also I have to twist the throttle about a quarter turn just to get it to start.
Assuming stock main jet havent opened the carbs up.

[Gordon]

for normal running, once warm, the choke lever should be pressed down(closed).

"Choke closed" means that the choke plates are closing off the air inlets, richening the mixture.  "Choke open" means that they're turned sideways allowing for maximum air flow and normal fuel mixture.  I know I'm being nit-picky about this, but it's an important distinction, and one that has confused many people on this forum in the past, causing them to think there's something wrong with their engine, when really all that was wrong was they were trying to run the engine at normal operating temperature with the choke closed, when it should have been open.

[flybox1]

get into your carbs dude!  
i'm betting you've got some sht in there blocking the tiny holes on the emulsion tubes under the main jets.
its keeping your fuel from atomizing.

bench synch the slides...
set your floats to 24mm, drink 2 beers and get back to us in the morning.  

Yes, Gordon...you are correct.
your choke LEVER should be UP when starting, and then pressed DOWN when warming/warmed up.
you'll be riding with it in the DOWN position.....if you lift the choke lever, you will starve and kill your engine.

[Burnboy]

carbs are apart now, cleaned every jet and port I could. About to set check float height, slow jets are #35, not sure how to get the main jet out, looking tat up now.

[Gordon]

Once the bowl is removed, the main jet is only held in by the friction of the o-ring and possibly varnish that's built up around it.  The emulsion tube above it should just fall out once the main jet is removed, but often they're stuck in with varnish, too.  A dirty and clogged emulsion tube is a common cause of running problems. 

[flybox1]

the main is a press-in, and is held in by an o-ring and the butterfly spring pressure against the bowl.  should pull right out after the butterfly spring is removed, but if not, go easy with some pliers, and give her a pull/twist straight out being careful not to bend or you'll crack its seat.
The emulsion tube is underneath, and can be pressed out from the slide and needle side (after you remove the slide) if it doesnt fall out.  i bet its nasty in there    clean the emulsion tube and all its tiny holes.