Only runs with choke on: Things to look for?

[Chris Cochran]

Ok, it'll run with the choke on full-down-to-three quarter's full, then dies. From what I've read this indicates that it's running lean. I haven't yet tried looking for air leaks. If that seems to be the issue then I know what to do.

But, if there are no apparent air leaks, am I correct in assuming that I need to turn the underside pilot screws? Right now they are all set on exactly two turns out. Would turning them IN richen up the mixture?

[GrandpaDenny]

Is this when the bike is cold, or when it's warmed up?

[Chris Cochran]

This is after it has run initially on the choke for a while. Am not sure exactly what the operational temp level is because right now the temp gauge isn't working, but even after it's been running for a good 10 minutes it'll croak once the choke goes below, oh, say 3/4 open.

Note: I have a house fan blowing on the radiator so it won't OVER-heat, though.

[Conrad]

Is the air intake and filter box fully assembled?
And does giving it a little throttle make a difference?

[Chris Cochran]

Airboxes are fully assembled and giving it gas tends to shut it off, or at least seriously stumble in that direction.

[Conrad]

Sounds a lot like lean. Vacuum line hooked up to ignition box i assume?

[Chris Cochran]

Yes, the vacuum line is hooked up.
So, in the next few days I'll have time to test for air leaks. If that comes up as not an issue, then I guess I'll give the pilot screws a tweak. Closing them richens it up I think.
Does this sound right?

[Conrad]

I'm not certain which pilot screws you mean, and I'm no expert on these particular carbs. However, they all work basically the same way. If a screw is metering air, then typically opening (unscrewing) will produce a leaner condition, closing (tightening) will produce a richer condition.
I would definitely check for vacuum leaks before messing with any adjustments.

I've also seen engines that will only run choked because floats are set too low. The "choke" is actually an enricher circuit which allows fuel to bypass the jets somewhat, and the pickup for it is near the bottom of the float bowl.

[Chris Cochran]

As I understand it, pilot jets, when initially installing them, are generally bottomed out first (gently) and then backed out to 2 turns. This is what I did when putting them back together after a full disassembly/cleaning. All four are set at two turns out right now.

I noticed when I first took them apart that carb #1's jet was bottomed all the way down and carb #2's jet was maybe 1/2 a turn out from the bottom. I don't remember the other two but I think they were just about set at two turns each. I thought this was rather weird. The bike didn't run at the time because the carbs were seriously gunked up with green residue from sitting for five years with ancient gas in them. So I couldn't test run it any.

[cushman eagle]

As I understand it, pilot jets, when initially installing them, are generally bottomed out first (gently) and then backed out to 2 turns. This is what I did when putting them back together after a full disassembly/cleaning. All four are set at two turns out right now.

I noticed when I first took them apart that carb #1's jet was bottomed all the way down and carb #2's jet was maybe 1/2 a turn out from the bottom. I don't remember the other two but I think they were just about set at two turns each. I thought this was rather weird. The bike didn't run at the time because the carbs were seriously gunked up with green residue from sitting for five years with ancient gas in them. So I couldn't test run it any.

Chris,since the carbs were gunked up that bad,is it possible they still are partially plugged up

[Chris Cochran]

Doubtful. They were taken down pretty completely.

[cushman eagle]

Doubtful. They were taken down pretty completely.

Chris,when you went through your cabs,did you check the condition of the diaphragms and if the vacuum pistons are free to slide up in their bores?
They need to slide up to lift the needles,and enrich the fuel mixture
Can you see the slides lift looking through the airbox as you give throttle?
And do the diaphragms receive the vacuum signal to lift as you open the throttle?
I had to go through that about 23 years ago when I bought a Suzuki GS1100GKZ which had stale fuel and gummed up carbs,and sheared splines in the rear wheel.

[Chris Cochran]

The diaphragms are not damaged nor have any holes in them, that much I know. They seemed to slide easily enough when I had it apart enough to mess with them although I have not "watched" them in operation. That section of the carbs, as all sections, were thoroughly cleaned, though.

I haven't looked through the lower air box to actually see them working and woe as I am to take the upper box off again, I suppose I have nothing to lose by doing so at this juncture of things.

This thought may be going off on a tangent: One of the standard things to check for are air leaks and there are all sorts of places for air leaks to happen on the air box side of the carbs what with all of the rubber tubes and all. I've recently seen a posting for a Voyager for sale in one of the FaceBook groups where the air boxes were removed, and it had four pod filters on instead. This would seem to essentially eliminate any possibility for air leaks in this area and make it a hell of a lot more simple to work on the carbs. I'm not sure how much jiggling they (the carbs) would do though since whatever physical support they get from the lower air box would be gone, but otherwise they seem like a good idea. Even if you use them for only the initial re-installation and carb tuning, then re-install the full upper/lower airboxes for actual operation, they may be a good idea. That way if you get the carbs running right and then, after putting the airboxes back on, they run like crap, you'll KNOW it's an air leak somewhere in that area.

Since I don't see them more in any postings anywhere it would seem to not be a popular modification. Thoughts?

[triton28]

While the operating characteristics of an engine with/without any air boxes has been the topic of many posts it should be noted that what is known as an "air leak" generally occurs downstream/after the venturi/throttle plate of a carburetor. Nothing before the intake mouth of a carburetor would be classified as an "Air leak" provided of course that all components/hoses of the carburetor itself are accounted for/mounted/adjusted and or connected as per design.
An "air leak" causes problems due to the fact that it corrupts the 15:1 air-fuel mixture after the charge of air and fuel leaves the carburetor, ergo most leaks are between the back of the carburetor and the cylinder head in the case of our Voyager XII design. 4 rubber carb holders in our case.
But I am sure you already know all this gobbledeegoop so IMHO you still have an idle passage/pilot jet problem with your carb bodies. I say this because at RPM below say 1000 only the pilot jets control the major contribution to the :1 portion of the 15:1 fuel mixture. Once the throttle plates are opened then the diaphragms start to raise the jet needles in the main jets sequentially as throttle is further called upon by the operator.
There is a transition point in the RPM range where the pilot jet fuel charge is transitioning to the main jets, ( by the diaphragms lifting), and that point is crucial for the pilot jets to be at the 15:1 mixture to effect a smooth transition to the main jet needles. Any unintended downstream increase in air content, read "air leak" here, will cause a corresponding falter in the engine's RPM as this transition occurs. This paragraph presupposes of course that the pilot jets/internal passages are in no way blocked.
Also, an unintended leak would affect the idling only characteristics as well but unless it was of major proportions the engine would still idle, albeit rough and possibly sputtering and popping back into the airbox.
You don't say if you used an ultrasonic cleaner when you cleaned the carbs. Once I had to run bodies 2 times to get all the varnish in the internal passages out. After the 2nd time all was well but until then it drove me around the bend. Now I automatically do 2 cycles in the bath.
Also Chris the external needle tipped screws you spoke of are pilot air screws as opposed to the internal, brass orificed pilot fuel jets. Regardless of the terminology though, 2 turns out from soft bottoming for the pilot air screws should be approximate enough to at least permit the engine to idle in some form.
Now for the obvious, and please do not mistake this as me being flippant, but you have tried winding the throttle stop screw knob in to ensure the throttle plates are at a degree of opening to support idling, right?
Once you get the carbs working well you will definitely be a "carb master" after all the problems you are having. I wish you luck in your endeavors. Sorry I can't be of more tangible help, regards,
Dave

[GrandpaDenny]

Now for the obvious, and please do not mistake this as me being flippant, but you have tried winding the throttle stop screw knob in to ensure the throttle plates are at a degree of opening to support idling, right?

Good answer, Dave. The idle speed knob is on the left side, well, having had the carb apart he surely knows where it is perhaps it's screwed in too far?

[Nails]

They seemed to slide easily enough

This has been discussed before. Polishing these is necessary. I use crumpled aluminum foil after a ridiculously careful ULTRASONIC cleaning.

A quick way to identify air leaks is to spray WD40 on the boots to see if it causes an engine miss. As Dave says, this is the engine-side boot.

Are the nipples rotten that cover the ports used to synch the carbs?

[Chris Cochran]

No, they are in fine shape. Now if I can just get some warm weather. It was 28 degrees when I got up this morning and stayed in the low 40s all day.