installing emulsion tubes

Hi all. During my recent carb cleaning, I (among other things) removed, cleaned, and reinstalled the emulsion tubes. When reinstalling, I made sure the guide pin was aligned, pushed the tube down until it felt fully-seated, and screwed the main jet into the bottom of it. What's bugging me is that it seems like for more than one carb, the tube pushed down further than it was when I removed it. I may be delirious, but what is the proper position for these emulsion tubes? Show it be inserted as far as possible, or until the bottom aligns with something, or should the main jet align with something? Is it possible that it could be too far down, resulting in the main jet being too low in the bowl and causing it to run too rich?

Also, taking a look at the exploded view that bigfitz52 posted (bike is a xj550, so Mikuni BS28 carbs) I see a main jet washer. I don't recall seeing a washer here on any of the carbs. I suppose it's possible that it was stuck to the main jet in all 4 cases, or it stayed behind in the opening, or that a PO screwed up and left them out.

Current symptom: starts pretty easily, runs ok (not great) up to about 3k, really struggles to get above 3k.

 

There is supposed to be a washer under the mains, not the smaller ones (unless mine are missing)

They should all come out where the larger part of the tube is about flush and the smaller diameter opening stick up a bit into the throat.

Seems if the washers were missing, yes it'd pull the tubes down farther when you tightened, and leave the needles higher than they should be in the bore...rich as hell, I'd suspect...

 

You know what? My head is about to explode from my own problems right now, and I may not be thinking right.

Disregard my answer except for the fact that there is supposed to washers on them.

Someone will know the correct answer to the rest...sorry...

 

That explains the extra fuel but where is it getting the air from to rev like that? We will see when you get the copper sealing washers back on under the mains.

MN

 

Well, what can you say about previous owners? Main jet washers were definitely missing across the board. Local dealership actually had them, so five bucks later got them installed. Idle mix circuits had a grand total of two o-rings and two washers between all four carbs. Anyway, got all that to look like its supposed to and now the bike will actually rev. Pulls pretty strong between 3k and 5k. Haven't had it above 5k or 40mph on the street, call me chicken due to riding in shorts and a t-shirt with the wind in my eyes.

I can't really explain the physics of it, though. Seems like the lack of a main jet washer would have raised the jet higher, which would have increased the penetration of the needle, which would have impeded the flow of fuel and actually made it leaner. But you can't argue with results, it revs now, the plugs look better, and it actually likes choke now when it's cold.

My question now is: How should it sound when it idles?

Should it be a very smooth and consistent purr, or should it be more of the blurbling sound that a Harley makes when it idles? It does idle, but it's more of the blurbling thing. I've tried to both sync and colortune it, but the fluctuations make it challenging when it's not a smooth purr. The colortune is blue but with frequent flashes of yellow. Does this mean it's missing, and then the following combustion stroke is too rich? Would this symptom on all 4 cylinders point to an electrical problem, or would you still suspect the carbs? Incidently, the electrical system is still stock, including the original fuse panel. I do intend to do something about it, just haven't gotten that far yet. Original coils/caps, but the secondary side does measure within spec.

Also, evidently my YICS passage is pretty nasty. I played hell getting the tool in there, couldn't get the bike to run well enough to sync it with the ports blocked, and destroyed the seals on the tool getting it back out. Looks like I will need to acquire a new set of seals, along with the necessary tools to clean that passage out. Anyone ever try running a long drill bit thru there? Just curious. So right now it's synced as well as I could get it without blocking the ports, although the fluctuations are much bigger than I would like.

The good news is I'm getting really good at putting the rack back on the bike. First time took a good hour with help, and now the 3rd time took me about 15 minutes by myself.

 

You need a Hoppe gun cleaning kit with the extensions, and brass brushes. Spray carb cleaner in the passage and use the handle and extensions to clean the passage out.

 

+1 on the gun cleaning kit.

Ime the idle wont be dead smooth but should be relatively close to that. It definitely shouldn't sound like a Harley.