Goofy 550E/ES Siamese Carb QandA session

[Guest]

Hey guys,

Working on an 86 550ES for a friend and fellow GSR. Had to do a motor transplant, and yes the valves on the "new" motor are adjusted. The battery is questionable, but i will be tending to that.

Here, however, is the deal:

After transplanting the motor, we got the bike (after fighting with the battery) to fire and run. It was taken up the road for a good ways, and the comment was that the bike seemed flat. I did not get the chance to test ride it myself. Had to return TODAY (previous engagement was a couple weeks ago) to find and repair an oil leak that cropped up (turned out to be another funky 16v 550 thing...) Fixed that and then took it up the road MYSELF. Indeed, the bike stumbles down low. Seemed rich. Took it back to the garage, and pulled the plugs. ONE and TWO are black and fluffy, RICH. THREE and FOUR look pretty good, maybe a HAIR on the lean side. Now, I know that spark for one and two is kinda weak. But that is not amazing to me, because i know the battery is kinda weak. I have seen it happen before, but why or how or would the faulty battery cause only TWO cylinders not to fire right? Hrmmm maybe, but prolly not. I dont know these carbs very well. They are goofy to me. The bike ran fine with the previous motor, and it only sat for a couple weeks before we got the new motor in it and got it running again. Would that be long enough to gumm up the carbs?? And if so, wouldnt they be LEAN rather than RICH??? I am a bit stumped, and I would like anyone who knows more about these carbs to weigh in a bit on their design. Ive played with the adjustment screws, and got no real success out of doing so. Also, when you give the bike choke, it bogs out, another sign that it is rich.....any help or advise would be appreciated. I will get a new batt, and run some seafoam thru the carbs with the new batt and see what happens, but im really thinking something funky is happening with the carbs.

Thanks guys


TCK

[rapidray]

Have you done a compression test or a leakdown on the motor to see if 1 & 2 are in worse condition than 3 & 4? Process of elimination! Ray.

[TheCafeKid]

Its not oil, its carbon fouling. The bike's pipe temps are within 30*F of eachother, and yeah i know thats not a great test. I suppose i can do a compression test on it, but I am pretty sure its the carbs. Or rather, CARB. It doesnt burn oil, there is no oil smell or colour in the exhaust, it hasnt used any oil, so i dont think its a compression issue. BUT, i will add it to the list of stuff to check. The question really more pertained to someone who knew that carbset and how they are set up. They have two slides in each carb, but both are actuated, from what i can tell by the same diaphram. Do they have on main jet, or two seperate?? Etc etc. Basicly, I would like to know what im getting into should i have to rebuild these carbs. Ive never dealt with them before. Otherwise, im pretty sure i can figure whatever else out. Thanks tho Ray

[SqDancerLynn1]

the fact that the carbs were off & probably turned upside down I would start by doing another cleaning. Then maybe swapping the coils side to side. Make sure the choke is adjusted & rubber plungers are sealing

[chef1366]

You didn't do a compression check???
Hack

[GSJim69]

These carbs share the body, slide diaphragm, choke and float. All the jets are separate. Siamese is a good description of these carbs.

As far as the one and two running rich, I would suspect the float height or something (rust) stuck under the float needle.

I have done two sets of these carbs now. Let me know if you have any questions.

[TheCafeKid]

These carbs share the body, slide diaphragm, choke and float. All the jets are separate. Siamese is a good description of these carbs.

As far as the one and two running rich, I would suspect the float height or something (rust) stuck under the float needle.

I have done two sets of these carbs now. Let me know if you have any questions.

Ohhh Ok. I wasnt sure how they were set up, kinda wanted some info before i cracked them open, if i have to. Good point on the floats or valves being stuck. Thats certainly a possibility. Thanks

[TheCafeKid]

You didn't do a compression check???
Hack

Yes, yes i am a hack. Most times, an adequate hack, but a hack nonetheless.

[Old Colt]

Ohh come on CK, at least use the excuse that you do not have the compression adapter for the small sparkplugs with you.

The ignition is shared as 1&4 and 2&3

The carbs are 1&2 and 3&4

I would not expect weak spark on 1&2 unless it has to do with coil polarity. That would be the positive spark being more or less powerful than the negative spark on the two coil outputs.

Were the exhaust temps in a pattern or just one low one?

I would open up the carbs and check the float area for deposits and inspect the diaphragms. But a general flat feeling could be timing, mixture or compression issues. Or as I recently had, an exhaust plugged by a nest.

[TheCafeKid]

Ohh come on CK, at least use the excuse that you do not have the compression adapter for the small sparkplugs with you.

The ignition is shared as 1&4 and 2&3

The carbs are 1&2 and 3&4

I would not expect weak spark on 1&2 unless it has to do with coil polarity. That would be the positive spark being more or less powerful than the negative spark on the two coil outputs.

Were the exhaust temps in a pattern or just one low one?

I would open up the carbs and check the float area for deposits and inspect the diaphragms. But a general flat feeling could be timing, mixture or compression issues. Or as I recently had, an exhaust plugged by a nest.

*Sigh* i appreciate the suggestions guys. But it is NOT a compression issue. Spark on one and two i know is weak, because i only checked one and two for spark. Ive rebuit, worked on, and cussed at enough of these bikes to know what the SOP for trackin down issues, and symptoms of each. When I say its flat, i mean its breaking up, because its rich on two cylinders. I am/was pretty sure it was a carb issue, but i cannot be ABSOLUTELY sure untill i have a good battery in there. You're talking about polarity of coils and all that nonesense. Its a nearly dead battery. I know the spark is weak because of that. My question had more to do with the SET UP of the carbs, as ive never worked on them before and simply wanted to know if there was something crazy about them other than the siamesed slides and diaphrams...

[Old Colt]

I would not say there are any special issues or procedures with the dual carbs. As far as balancing you just have the one adjustment that affects left or right being strong or weak. Other than that treat them like any other CV carb.

[Bones]

Het TCK.

Yes, each set of carbs has two pilot jets, two main jets, one float, and one float needle. The throttle slides (on one set) do work off of the same diaphram.

The pilot jets are in the middle of the carb (side by side) and the main jets are closer to the outsides of the carb set.

Just so you know.

Bones

[robertbarr]

Hey, I have a question:

Did you (or anyone else with these siamesed 550 carbs) use my standard CV O-ring kit, and if so, how did it work out? I have a person looking to repair his '83 550.

I recall someone using my kit, but I don't recall who it was or how it turned out.

TIA.

RB

[Calvin Blackmore]

I did Robert.
it worked out fine and there was a noticeable improvement in idle and throughout the RPM range.

pretty sure the old o-rings had to be marginal as they were at or below the surface of their grooves int he manifolds.

[robertbarr]

I did Robert.
it worked out fine and there was a noticeable improvement in idle and throughout the RPM range.

pretty sure the old o-rings had to be marginal as they were at or below the surface of their grooves int he manifolds.

Thanks, but are you talking about the intake O-rings or the carb kit? It sounds like the former. (I don't really recall what I sold you back then...).

RB